Method and apparatus for communication in wireless communication system

ABSTRACT

The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. An embodiment of the present disclosure relates to a method and an apparatus for transmitting data in a next-generation mobile communication system.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of U.S. Ser. No. 15/966,966, whichwas filed in the U.S. Patent and Trademark Office on Apr. 30, 2018, andclaims priority under 35 U.S.C. § 119(a) to Korean Patent ApplicationSerial number 10-2017-0055205, filed on Apr. 28, 2017 in the KoreanIntellectual Property Office, the entire disclosure of which isincorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates, generally, to a communication method,and more particularly, to a method and apparatus configured forcommunication in a next-generation wireless communication system.

2. Description of the Related Art

To meet the demand for wireless data traffic, which has increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system, also called a‘beyond 4G network’ or a ‘post LTE system’. The 5G communication systemimplements higher frequency (mmWave) bands, e.g., 60 GHz bands, toaccomplish higher data rates. To decrease propagation loss of the radiowaves and increase the transmission distance, beamforming, massivemultiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO),array antenna, an analog beam forming, large scale antenna techniquesare contemplated in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, hybrid frequency-shift keying (FSK) andquadrature amplitude modulation (QAM) (FQAM) and sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM), andfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA) as an advanced access technologyhave been developed.

Moreover, the Internet is now evolving to the Internet of things (IoT)where distributed entities, such as things, exchange and processinformation without human intervention. The Internet of everything(IoE), which is a combination of the IoT technology and the big dataprocessing technology through connection with a cloud server, hasemerged. As technology elements, such as sensing technology,wired/wireless communication and network infrastructure, serviceinterface technology, and security technology have been used for IoTimplementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that can be used for collecting andanalyzing data generated among connected things. IoT may be applied to avariety of fields including smart home, smart building, smart city,smart car or connected cars, smart grid, health care, smart appliancesand advanced medical services through convergence and combinationbetween existing information technology (IT) and various industrialapplications.

Various attempts have been made to apply 5G communication systems to IoTnetworks. For example, technologies such as a sensor network, MTC, andM2M communication may be implemented by beamforming, MIMO, and arrayantennas. Application of a cloud RAN is also an example of convergencebetween the 5G technology and the IoT technology.

Further, a next-generation mobile communication system, when a radiolink control (RLC) layer performs segmentation operation, may split anRLC service data unit (SDU) into several segments based on a segmentoffset (SO) field. For each segment, an SO field is included in an RLCheader to indicate at what location of the original RLC SDU thesegmentation has come. However, since an SO field may have a size ofabout 2 bytes, inclusion of such an SO field for each segment mayincrease overhead during data transmission and may result in a waste ofradio resources.

SUMMARY

The disclosure has been made to address at least the disadvantagesdescribed above and to provide at least the advantages described below.

Accordingly, an aspect of the disclosure provided a method for reducingoverhead in a wireless communication system.

An aspect of the disclosure is to provide a method for transmittingpacket-duplicated data introduced in a next-generation mobilecommunication system. A scheduler can be required to determine how muchdata is to be duplicated. That is, duplicated data should be transmittedfrom different time resources through different carriers or differentmedium access control (MAC) PDUs, and transmission resources should notbe allocated so that all data are transmitted from one MAC PDU.Accordingly, an aspect of the disclosure provides a method for mappingthe method for transmitting the packet-duplicated data newly introducedin the next-generation mobile communication system to different logicalchannel groups.

An aspect of the disclosure provides a method for not increasingcomplexity caused by unnecessary packet duplication, i.e., when packetduplication introduced in the next-generation mobile communicationsystem is used.

An aspect of the disclosure provides a method for optimizing the SOfield when the RLC layer performs segmentation in the next-generationmobile communication system. Overhead during the data transmission canbe reduced, and the radio resources can be efficiently used.

Further, according to an aspect of the disclosure, the duplicated datacan be transmitted from different time resources through differentcarriers or different MAC PDUs, and thus the reliability can be improvedthrough the packet duplication. When the duplicated data uses the samelogical channel group, the resources for the duplicated data can beallocated by introducing the new buffer status report.

An aspect of the disclosure, by introducing a method in which theterminal selects the transmission path or selectively performs thepacket duplication in accordance with the channel situation in thenext-generation mobile communication system, provides the communicationmethod suitable to the channel situation can be used, and unnecessarypacket duplication can be prevented to reduce signaling and systemcomplexity.

In accordance with an aspect, a method is provided for a transmittingdevice in a wireless communication system. The method includes obtaininga radio link control (RLC) service data unit (SDU) from an upper layer;generating an unacknowledged mode (UM) data (UMD) protocol data unit(PDU) for the RLC SDU, the UMD PDU including a UMD PDU header; andtransmitting the UMD PDU to a receiving device. The UMD PDU headerincludes a segmentation information (SI) field and a reserved (R) field,in case that the UMD PDU includes a complete RLC SDU which is the RLCSDU. The UMD PDU header includes an SI field, an R field and a sequencenumber (SN) field, in case that the UMD PDU includes an RLC SDU segmentwhich is a segment of the RLC SDU.

In accordance with another aspect, a method performed is provided for areceiving device in a wireless communication system. The method includesreceiving, from a transmitting device, an unacknowledged mode (UM) data(UMD) protocol data unit (PDU) for a radio link control (RLC) servicedata unit (SDU), the UMD PDU including a UMD PDU header; and identifyinga UMD PDU header from the UMD PDU. The UMD PDU header includes asegmentation information (SI) field and a reserved (R) field, in casethat the UMD PDU includes a complete RLC SDU which is the RLC SDU. TheUMD PDU header includes an SI field, an R field and a sequence number(SN) field, in case that the UMD PDU includes an RLC SDU segment whichis a segment of the RLC SDU.

In accordance with another aspect, a transmitting device is provided ina wireless communication system. The transmitting device includes atransceiver; and a controller configured to obtain a radio link control(RLC) service data unit (SDU) from an upper layer, generate anunacknowledged mode (UM) data (UMD) protocol data unit (PDU) for the RLCSDU, the UMD PDU including a UMD PDU header, and transmit the UMD PDU toa receiving device via the transceiver. The UMD PDU header includes asegmentation information (SI) field and a reserved (R) field, in casethat the UMD PDU includes a complete RLC SDU which is the RLC SDU. TheUMD PDU header includes an SI field, an R field and a sequence number(SN) field, in case that the UMD PDU includes an RLC SDU segment whichis a segment of the RLC SDU.

In accordance with another aspect, a receiving device is provided in awireless communication system. The receiving device includes atransceiver; and a controller configured to receive, from a transmittingdevice via the transceiver, an unacknowledged mode (UM) data (UMD)protocol data unit (PDU) for a radio link control (RLC) service dataunit (SDU), the UMD PDU including a UMD PDU header, and identify a UMDPDU header from the UMD PDU. The UMD PDU header includes a segmentationinformation (SI) field and a reserved (R) field, in case that the UMDPDU includes a complete RLC SDU which is the RLC SDU. The UMD PDU headerincludes an SI field, an R field and a sequence number (SN) field, incase that the UMD PDU includes an RLC SDU segment which is a segment ofthe RLC SDU.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainembodiments of the disclosure will be more apparent from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1A is a diagram of a structure of a long term evolution (LTE)system, according to an embodiment;

FIG. 1B is a diagram of a radio protocol structure of an LTE system,according to an embodiment;

FIG. 1C is a diagram of a next-generation mobile communication system,according to an embodiment;

FIG. 1D is a diagram of a radio protocol structure of a next-generationmobile communication system, according to an embodiment;

FIG. 1E is a signaling diagram in which a terminal is switched from aradio resource control (RRC) connected mode to an RRC idle mode and inwhich the terminal is switched from the RRC idle mode to the RRCconnected mode, according to an embodiment;

FIG. 1F is a diagram of a segmentation operation of an RLC layer,according to an embodiment;

FIGS. 1GA and 1GB are diagrams of an RLC header applicable, according toan embodiment;

FIGS. 1HA and 1HB are flowcharts of a method in which a terminalconfigures an RLC header, according to an embodiment;

FIGS. 1IA and 1IB are diagrams of an RLC header applicable, according toan embodiment;

FIGS. 1JA and 1JB are flowcharts of a method in which a terminalconfigures an RLC header, according to an embodiment;

FIG. 1K is a diagram of a terminal, according to an embodiment;

FIG. 1L is a diagram of a base station in a wireless communicationsystem, according to an embodiment;

FIG. 2A is a diagram of an LTE system, according to an embodiment;

FIG. 2B is a diagram illustrating a radio protocol structure of an LTEsystem for reference in explaining the present disclosure;

FIGS. 2CA and 2CB are diagrams illustrating multi-connection and carrieraggregation operations of an existing LTE system, according to anembodiment;

FIG. 2D is a diagram of a next-generation mobile communication system,according to an embodiment;

FIG. 2E is a diagram of a data transmission operation through packetduplication, according to an embodiment;

FIG. 2F is a diagram of a first data packet duplicate transmissionoperation, according to an embodiment;

FIG. 2G is a diagram of a first data packet duplicate transmissionoperation, according to an embodiment;

FIG. 2H is flowchart of a method to which a first data packet duplicatetransmission operation is applied, according to an embodiment;

FIG. 2I is a flowchart of a method which a second data packet duplicatetransmission operation, according to an embodiment;

FIG. 2J is a flowchart of a method a first data packet duplicatetransmission operation of a terminal, according to an embodiment;

FIG. 2K is a flowchart of a method of a second data packet duplicatetransmission operation of a terminal, according to an embodiment;

FIG. 2L is a diagram of a terminal, according to an embodiment;

FIG. 2M is a diagram of a base station, according to an embodiment;

FIG. 3A is a diagram of an LTE system, according to an embodiment;

FIG. 3B is a diagram of a radio protocol structure of an LTE system,according to an embodiment;

FIGS. 3CA and 3CB are diagrams of multi-connection and carrieraggregation operations of an existing LTE system, according to anembodiment;

FIG. 3D is a diagram of a next-generation mobile communication system,according to an embodiment;

FIG. 3E is a flowchart of a method of a first operation in which a basestation determines path selection and duplicate transmission type,according to an embodiment;

FIG. 3F is a flowchart of a method of a second operation in which aterminal determines path selection and duplicate transmission type,according to an embodiment;

FIG. 3G is a flowchart of a method of a first operation of a terminal,according to an embodiment;

FIG. 3H is a flowchart of a method of a second operation of a terminal,according to an embodiment;

FIG. 3I is a block of a terminal, according to an embodiment;

FIG. 3J is a diagram of a base station, according to an embodiment;

FIG. 4A is a diagram of a next-generation mobile communication system,according to an embodiment;

FIG. 4B is a diagram of changing system information in an LTEtechnology, according to an embodiment;

FIG. 4C is a diagram of a method for performing segmentation information(SI) validity check before RRC connection establishment in case ofapplying an eDRX technology in an LTE technology, according to anembodiment;

FIG. 4D is a diagram of a method for indicating whether an SI update isnecessary by transmitting a paging in an extended modification period incase of applying an eDRX technology in an LTE technology, according toan embodiment;

FIG. 4E is a diagram explaining the concept of configuration of aplurality of modification periods according to a fourth embodiment ofthe present disclosure;

FIG. 4F is a flowchart of a method of updating system information basedon a plurality of modification periods, according to an embodiment;

FIG. 4G is a flowchart of a method of an operation of a terminal,according to an embodiment;

FIG. 4H is a flowchart of a method of an operation of a base station,according to an embodiment;

FIG. 4I is a diagram of a terminal, according to an embodiment; and

FIG. 4J is a diagram of a base station, according to an embodiment.

DETAILED DESCRIPTION

Embodiments of the disclosure will be described herein below withreference to the accompanying drawings. However, the embodiments of thedisclosure are not limited to the specific embodiments and should beconstrued as including all modifications, changes, equivalent devicesand methods, and/or alternative embodiments of the present disclosure.In the description of the drawings, similar reference numerals are usedfor similar elements.

The terms “have,” “may have,” “include,” and “may include” as usedherein indicate the presence of corresponding features (for example,elements such as numerical values, functions, operations, or parts), anddo not preclude the presence of additional features.

The terms “A or B,” “at least one of A or/and B,” or “one or more of Aor/and B” as used herein include all possible combinations of itemsenumerated with them. For example, “A or B,” “at least one of A and B,”or “at least one of A or B” means (1) including at least one A, (2)including at least one B, or (3) including both at least one A and atleast one B.

The terms such as “first” and “second” as used herein may usecorresponding components regardless of importance or an order and areused to distinguish a component from another without limiting thecomponents. These terms may be used for the purpose of distinguishingone element from another element. For example, a first user device and asecond user device may indicate different user devices regardless of theorder or importance. For example, a first element may be referred to asa second element without departing from the scope the disclosure, andsimilarly, a second element may be referred to as a first element.

It will be understood that, when an element (for example, a firstelement) is “(operatively or communicatively) coupled with/to” or“connected to” another element (for example, a second element), theelement may be directly coupled with/to another element, and there maybe an intervening element (for example, a third element) between theelement and another element. To the contrary, it will be understoodthat, when an element (for example, a first element) is “directlycoupled with/to” or “directly connected to” another element (forexample, a second element), there is no intervening element (forexample, a third element) between the element and another element.

The expression “configured to (or set to)” as used herein may be usedinterchangeably with “suitable for,” “having the capacity to,” “designedto,” “adapted to,” “made to,” or “capable of” according to a context.The term “configured to (set to)” does not necessarily mean“specifically designed to” in a hardware level. Instead, the expression“apparatus configured to . . . ” may mean that the apparatus is “capableof . . . ” along with other devices or parts in a certain context. Forexample, “a processor configured to (set to) perform A, B, and C” maymean a dedicated processor (e.g., an embedded processor) for performinga corresponding operation, or a generic-purpose processor (e.g., acentral processing unit (CPU) or an application processor (AP)) capableof performing a corresponding operation by executing one or moresoftware programs stored in a memory device.

The terms used in describing the various embodiments are for the purposeof describing particular embodiments and are not intended to limit thedisclosure. As used herein, the singular forms are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. All of the terms used herein including technical orscientific terms have the same meanings as those generally understood byan ordinary skilled person in the related art unless they are definedotherwise. The terms defined in a generally used dictionary should beinterpreted as having the same or similar meanings as the contextualmeanings of the relevant technology and should not be interpreted ashaving ideal or exaggerated meanings unless they are clearly definedherein. According to circumstances, even the terms defined in thisdisclosure should not be interpreted as excluding the embodiments of thedisclosure.

The term “module” as used herein may, for example, mean a unit includingone of hardware, software, and firmware or a combination of two or moreof them. The “module” may be interchangeably used with, for example, theterm “unit”, “logic”, “logical block”, “component”, or “circuit”. The“module” may be a minimum unit of an integrated component element or apart thereof. The “module” may be a minimum unit for performing one ormore functions or a part thereof. The “module” may be mechanically orelectronically implemented. For example, the “module” according to thedisclosure may include at least one of an application-specificintegrated circuit (ASIC) chip, a field-programmable gate array (FPGA),and a programmable-logic device for performing operations which has beenknown or are to be developed hereinafter.

An electronic device according to the disclosure may include at leastone of, for example, a smart phone, a tablet personal computer (PC), amobile phone, a video phone, an electronic book reader (e-book reader),a desktop PC, a laptop PC, a netbook computer, a workstation, a server,a personal digital assistant (PDA), a portable multimedia player (PMP),a MPEG-1 audio layer-3 (MP3) player, a mobile medical device, a camera,and a wearable device. The wearable device may include at least one ofan accessory type (e.g., a watch, a ring, a bracelet, an anklet, anecklace, a glasses, a contact lens, or a head-mounted device (HMD)), afabric or clothing integrated type (e.g., an electronic clothing), abody-mounted type (e.g., a skin pad, or tattoo), and a bio-implantabletype (e.g., an implantable circuit).

The electronic device may be a home appliance. The home appliance mayinclude at least one of, for example, a television, a digital video disk(DVD) player, an audio, a refrigerator, an air conditioner, a vacuumcleaner, an oven, a microwave oven, a washing machine, an air cleaner, aset-top box, a home automation control panel, a security control panel,a TV box (e.g., Samsung HomeSync™, Apple TV™, or Google TV™), a gameconsole (e.g., Xbox™ and PlayStation™), an electronic dictionary, anelectronic key, a camcorder, and an electronic photo frame.

The electronic device may include at least one of various medicaldevices (e.g., various portable medical measuring devices (a bloodglucose monitoring device, a heart rate monitoring device, a bloodpressure measuring device, a body temperature measuring device, etc.), amagnetic resonance angiography (MRA), a magnetic resonance imaging(MRI), a computed tomography (CT) machine, and an ultrasonic machine), anavigation device, a global positioning system (GPS) receiver, an eventdata recorder (EDR), a flight data recorder (FDR), a vehicleinfotainment device, an electronic device for a ship (e.g., a navigationdevice for a ship, and a gyro-compass), avionics, security devices, anautomotive head unit, a robot for home or industry, an automatic tellermachine (ATM) in banks, point of sales (POS) devices in a shop, or anIoT device (e.g., a light bulb, various sensors, electric or gas meter,a sprinkler device, a fire alarm, a thermostat, a streetlamp, a toaster,a sporting goods, a hot water tank, a heater, a boiler, etc.).

The electronic device may include at least one of a part of furniture ora building/structure, an electronic board, an electronic signaturereceiving device, a projector, and various kinds of measuringinstruments (e.g., a water meter, an electric meter, a gas meter, and aradio wave meter). The electronic device may be a combination of one ormore of the aforementioned various devices. The electronic device mayalso be a flexible device. Further, the electronic device is not limitedto the aforementioned devices, and may include an electronic deviceaccording to the development of new technology.

Hereinafter, an electronic device will be described with reference tothe accompanying drawings. In the disclosure, the term “user” mayindicate a person using an electronic device or a device (e.g., anartificial intelligence electronic device) using an electronic device.

Hereinafter, terms and titles that are defined in the 3^(rd) generationpartnership project long term evolution (3GPP LTE) standards are used inthe disclosure.

However, the disclosure is not limited by the terms and titles, but canbe equally applied to systems following other standards. In thedisclosure, an evolved node B (eNB) may be used interchangeably with agNB (5G base station). That is, a base station described as the eNB maybe indicated as the gNB.

FIG. 1A is a diagram of an LTE system, according to an embodiment.

Referring to FIG. 1A, a RAN of an LTE system is composed of evolved nodeBs (eNBs, ENBs, node Bs, or base stations) 1 a-05, 1 a-10, 1 a-15, and 1a-20, a mobility management entity (MME) 1 a-25, and a serving-gateway(S-GW) 1 a-30. User equipment (a UE or terminal) 1 a-35 accesses to anexternal network through the ENBs 1 a-05 to 1 a-20 and the S-GW 1 a-30.

In FIG. 1A, the ENBs 1 a-05 to 1 a-20 correspond to existing node Bs ofa universal mobile telecommunications system (UMTS). The ENBs 1 a-05 to1 a-20 are connected to the UE 1 a-35 on a radio channel, and play amore complicated role than that of the existing node B. In the LTEsystem, since all user traffics including a real-time service, such as avoice over internet protocol (VoIP) through an internet protocol, areserviced on shared channels, devices performing scheduling throughsummarization of state information, such as a buffer state, an availabletransmission power state, and a channel state of each UE, are necessary,and the ENBs 1 a-05 to 1 a-20 control this. In general, one ENB controlsa plurality of cells. For example, in order to implement a transmissionspeed of 100 Mbps, the LTE system uses orthogonal frequency divisionmultiplexing (OFDM) in a bandwidth of 20 MHz as a radio accesstechnology (RAT). Further, the LTE system adopts an adaptive modulation& coding (AMC) scheme that determines a modulation scheme and a channelcoding rate to match the channel state of the terminal. The S-GW 1 a-30is a device that provides a data bearer, and generates or removes thedata bearer under the control of the MME 1 a-25. The MME is a devicethat controls not only mobility management of the terminal but alsovarious kinds of control functions, and is connected to the plurality ofENBs.

FIG. 1B is a diagram of a radio protocol structure in an LTE system,according to an embodiment.

Referring to FIG. 1B, in UE or an ENB, a radio protocol of an LTE systemis composed of a packet data convergence protocol (PDCP) 1 b-05 or 1b-40, an RLC 1 b-10 or 1 b-35, and a MAC 1 b-15 or 1 b-30. The PDCP 1b-05 or 1 b-40 controls IP header compression/decompression operations.The main functions of the PDCP are summarized as follows:

Header compression and decompression: robust header compression (ROHC)only;

Transfer of user data;

In-sequence delivery of upper layer physical data units (PDUs) at a PDCPreestablishment procedure for an RLC acknowledge mode (AM);

For split bearers in data communication (DC) (only support for an RLCAM): PDCP PDU routing for transmission and PDCP PDU reordering forreception;

Duplicate detection of lower layer SDUs at a PDCP reestablishmentprocedure for an RLC AM;

Retransmission of PDCP SDUs at handover and, for split bearers in DC, ofPDCP PDUs at a PDCP data-recovery procedure, for an RLC AM;

Ciphering and deciphering;

Timer-based SDU discard in an uplink; and The RLC 1 b-10 or 1 b-35reconfigures a PDCP PDU with a proper size and performs an automaticrepeat request (ARQ) operation and the like. The main functions of theRLC are summarized as follows:

Transfer of upper layer PDUs;

Error correction through an ARQ (only for AM data transfer);

Concatenation, segmentation, and reassembly of RLC SDUs (only forunacknowledged mode (UM) and AM data transfer);

Re-segmentation of RLC data PDUs (only for AM data transfer);

Reordering of RLC data PDUs (only for UM and AM data transfer);

Duplicate detection (only for UM and AM data transfer);

Protocol error detection (only for AM data transfer);

RLC SDU discard (only for UM and AM transfer); and

RLC reestablishment.

The MAC 1 b-15 or 1 b-30 is connected to several RLC layer devicesconfigured in one terminal, and performs multiplexing/demultiplexing ofRLC PDUs into/from MAC PDU. The main functions of the MAC are summarizedas follows:

Mapping between logical channels and transport channels;

Multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels;

Scheduling information reporting;

hybrid ARQ (HARQ) function (error correction through HARQ);

Priority handling between logical channels of one UE;

Priority handling between UEs by means of dynamic scheduling;

multimedia broadcast multicast services (MBMS) service identification;

Transport format selection; and

Padding.

The physical layer 1 b-20 or 1 b-25 performs channel coding andmodulation of upper layer data to configure and transmit OFDM symbols ona radio channel, or performs demodulation and channel decoding of theOFDM symbols received on the radio channel to transfer the demodulatedand channel-decoded symbols to an upper layer.

FIG. 1C is a diagram of a next-generation mobile communication system,according to an embodiment.

Referring to FIG. 1C, as illustrated, a RAN of a next-generation mobilecommunication system (NR or 5G) is composed of a new radio node B (NRgNB or NR ENB) 1 c-10 and a new radio core network (NR CN) 1 c-05. A newradio user equipment (NR UE or terminal) 1 c-15 accesses to an externalnetwork through the NR gNB 1 c-10 and the NR CN 1 c-05.

In FIG. 1C, the NR gNB 1 c-10 corresponds to an ENB of the existing LTEsystem. The NR gNB is connected to the NR UE 1 c-15 on a radio channel,and thus it can provide a superior service than the service of theexisting node B. Since all user traffics are serviced on shared channelsin the next-generation mobile communication system, a device thatperforms scheduling through consolidation of status information, such asa buffer state of UEs, an available transmission power state, and achannel state, is required, and a new radio node B NR NB 1 c-10 controlsthis operation. One NR gNB generally controls a plurality of cells. Inorder to implement ultrahigh-speed data transmission as compared withthe existing LTE, the NR gNB may have a bandwidth that is greater thanor equal to the existing maximum bandwidth, and a beamforming technologymay be additionally grafted in consideration of OFDM as an RAT. Further,an AMC scheme determining a modulation scheme and a channel coding rateto match the channel state of the UE is adopted. The NR CN 1 c-05performs functions of mobility support, bearer setup, and quality ofservice (QoS) configuration. The NR CN is a device that controls amobility management function of the UE, but also various kinds ofcontrol functions, and is connected to a plurality of ENBs. Further, thenext-generation mobile communication system may interlock with theexisting LTE system, and the NR CN is connected to an MME 1 c-25 througha network interface. The MME is connected to an ENB 1 c-30 that is theexisting ENB.

FIG. 1D is a diagram of a radio protocol structure of a next-generationmobile communication system, according to an embodiment.

Referring to FIG. 1D, in UE or an NR ENB, a radio protocol of thenext-generation mobile communication system is composed of an NR PDCP 1d-05 or 1 d-40, an NR RLC 1 d-10 or 1 d-35, and an NR MAC 1 d-15 or 1d-30. The main functions of the NR PDCP 1 d-05 or 1 d-40 may include thefollowing functions:

Header compression and decompression: ROHC only;

Transfer of user data;

In-sequence delivery of upper layer PDUs;

PDCP PDU reordering for reception;

Duplicate detection of lower layer SDUs;

Retransmission of PDCP SDUs;

Ciphering and deciphering; and

Timer-based SDU discard in an uplink.

As described above, reordering of the NR PDCP devices may meanreordering of PDCP PDUs received from a lower layer based on PDCPsequence numbers (SNs). The reordering may include transfer of data toan upper layer in the order of reordering, recording of lost PDCP PDUsthrough reordering, status report for the lost PDCP PDUs to atransmission side, and retransmission request for the lost PDCP PDUs.

The main functions of the NR RLC 1 d-10 or 1 d-35 may include followingfunctions:

Transfer of upper layer PDUs;

In-sequence delivery of upper layer PDUs;

Out-of-sequence delivery of upper layer PDUs;

Error correction through an ARQ;

Concatenation, segmentation, and reassembly of RLC SDUs;

Re-segmentation of RLC data PDUs;

Reordering of RLC data PDUs;

Duplicate detection;

Protocol error detection;

RLC SDU discard; and

RLC reestablishment.

As described above, in-sequence delivery of NR RLC devices may includein-sequence delivery of RLC SDUs received from a lower layer to an upperlayer. When one original RLC SDU is segmented into several RLC SDUs tobe received, the delivery may include reassembly and delivery of the RLCSDUs, reordering of the received RLC PDUs based on an RLC SN or a PDCPSN, recording of lost RLC PDUs through reordering, status report for thelost RLC PDUs to a transmission side, retransmission request for thelost PDCP PDUs, in-sequence delivery of only RLC SDUs just before thelost RLC SDU to an upper layer if there is the lost RLC SDU, in-sequencedelivery of all RLC SDUs received before a specific timer starts itsoperation to an upper layer if the timer has expired although there isthe lost RLC SDU, or in-sequence delivery of all RLC SDUs received up tonow to an upper layer if the timer has expired although there is thelost RLC SDU. Further, the RLC PDUs may be processed in the order oftheir reception (in the order of their arrival regardless of the orderof SNs), and may be transferred to the PDCP device in an out-of-sequencedelivery manner. With regard to the segments, one complete RLC PDU maybe reconfigured through reception of the segments stored in a buffer orto be received later, and then may be transferred to the PDCP device.The NR RLC layer may not include a concatenation function, and thefunction may be performed by an NR MAC layer or may be replaced by amultiplexing function of the NR MAC layer.

As described above, the out-of-sequence delivery of the NR RLC devicecan include a function of transferring the RLC SDUs received from alower layer directly to an upper layer in an out-of-sequence manner. Ifone original RLC SDU is segmented into several RLC SDUs to be received,the delivery may include reassembly and delivery of the RLC SDUs, andrecording of the lost RLC PDUs through storing and ordering the RLC SNsor PDCP SNs of the received RLC PDUs.

The NR MAC 1 d-15 or 1 d-30 may be connected to several NR RLC layerdevices configured in one UE, and the main functions of the NR MAC mayinclude the following functions:

Mapping between logical channels and transport channels;

Multiplexing/demultiplexing of MAC SDUs;

Scheduling information reporting;

HARQ function (error correction through HARQ);

Priority handling between logical channels of one UE;

Priority handling between UEs by means of dynamic scheduling;

MBMS service identification;

Transport format selection; and

Padding.

The NR PHY layer 1 d-20 or 1 d-25 may perform channel coding andmodulation of upper layer data to configure and transmit OFDM symbols toa radio channel, or may perform demodulation and channel decoding of theOFDM symbols received on the radio channel to transfer the demodulatedand channel-decoded symbols to an upper layer.

FIG. 1E is a signaling diagram in which a terminal is switched from anRRC connected mode to an RRC idle mode and a procedure in which theterminal is switched from the RRC idle mode to the RRC connected mode,according to an embodiment.

Referring to FIG. 1E, if a terminal (UE) transmitting/receiving data inan RRC connected mode does not transmit/receive data for a specificreason or for a predetermined time, a base station (gNB) may transmit anRRCConnectionRelease message to the UE to switch the UE to an RRC idlemode (at step 1 e-01). Thereafter, if data to be transmitted isgenerated, the UE of which connection is not currently set (idle modeUE) performs an RRC connection establishment process with the gNB. TheUE establishes backward transfer synchronization with the gNB through arandom access process (RAP), and transmits an RRCConnectionRequestmessage to the gNB (at step 1 e-05). The message contains an identifierof the UE and a connection establishmentCause.

The gNB transmits an RRCConnectionSetup message to the UE so that the UEsets the RRC connection (at step 1 e-10). The RRCConnectionSetup messagemay be set so as to optimally use a segment offset (SOI field as a shortSO field or a long SO field according to circumstances or to use onlythe long SO field when a segmentation operation is performed for eachservice/bearer/RLC device. Further, the RRCConnectionSetup messagecontains RRC connection configuration information, etc. The RRCconnection is also called signaling radio bearer (SRB), and is used totransmit/receive an RRC message that is a control message between the UEand the gNB.

The UE having set the RRC connection transmits anRRCConnectionSetupComplete message to the gNB (at step 1 e-15). Themessage includes a control message so called SERVICE REQUEST for the UEto request a bearer setup for a specific service from an MME. The gNBtransmits the SERVICE REQUEST message contained in theRRCConnectionSetupComplete message to the MME (at step 1 e-20), and theMME determines whether to provide the service requested by the UE. If itis determined to provide the service requested by the UE as the resultof the determination, the MME transmits an INITIAL CONTEXT SETUP REQUESTmessage to the gNB (at step 1 e-25). The INITIAL CONTEXT SETUP REQUESTmessage includes QoS information to be applied during data radio bearer(DRB) setup and security related information (e.g., security key orsecurity algorithm) to be applied to the DRB.

In order to set the security with the UE, the gNB exchanges aSecurityModeCommand message at step 1 e-30 and a SecurityModeCompletemessage at step 1 e-35 with the UE. If the security setup is completed,the gNB transmits an RRCConnectionReconfiguration message to the UE (atstep 1 e-40). The RRCConnectionReconfiguration message may be set so asto optimally use the SO field as the short SO field or the long SO fieldaccording to circumstances or to use only the long SO field when thesegmentation operation is performed for each service/bearer/RLC device.Further, the RRCConnectionReconfiguration message includes setupinformation of the DRB whereby user data is to be processed, and the UEsets the DRB by applying the information, and transmits anRRCConnectionReconfigurationComplete message to the gNB (at step 1e-45).

The gNB that has completed the DRB setup with the UE transmits anINITIAL CONTEXT SETUP COMPLETE message to the MME (at step 1 e-50), andthe MME that has received this exchanges an S1 BEARER SETUP message andan S1 BEARER SETUP RESPONSE message with an S-GW in order to set the S1bearer (at steps 1 e-55 and 1 e-60). The S1 bearer is a connection fordata transmission set between the S-GW and the gNB, and corresponds tothe DRB, in a one-to-one manner. If the above-described processes arecompleted, the UE transmits/receives data to/from the gNB through theS-GW (at steps 1 e-65 and 1 e-70). As described above, a general datatransmission process is briefly composed of three stages of RRCconnection setup, security setup, and DRB setup.

Further, the gNB may transmit an RRCConnectionReconfiguration message tothe UE in order to renew, add, or change the setup for a specific reason(at step 1 e-75). The message may be set so as to optimally use the SOfield as the short SO field or the long SO field according tocircumstances or to use only the long SO field when the segmentationoperation is performed for each service/bearer/RLC device.

FIG. 1F is a diagram of a segmentation operation of an RLC layer,according to an embodiment.

The disclosure provides an efficient RLC layer header structure andsegmentation operation.

More particularly, the first embodiment provides a procedure and amethod in which an RLC layer performs an SO-based segmentation operationwith respect to packets received from an upper layer. The providedmethod may perform an integrated segmentation operation without dividingthe segmentation operation into those in case of an initial transmissionand a retransmission. Further, it may be assumed that the RLC layer doesnot perform concatenation, that an SI field is introduced into an RLCheader to determine whether an RLC SDU that is a data part in the rearof the RLC header is a complete RLC SDU that has not been segmented, theforemost segmented RLC SDU segment, a middle segmented RLC SDU segment,or the last segmented RLC SDU segment, and that the RLC header does nothave a length field indicating a length.

Referring to FIG. 1F, the RLC layer receives a PDCP PDU (RLC SDU) (atstep 1 f-05) transferred from a PDCP layer that is an upper layer. TheRLC SDU may be processed to have a size indicated by a MAC layer, and ifit is segmented, an RLC PDU may be configured to include segmentationinformation of a header. The RLC PDU is composed of an RLC header and anRLC payload (RLC SDU). The RLC header may include an RLC PDU character(data or control information) and segmentation information, and mayfurther include a data/control (D/C) field, a polling (P) field, an SIfield, an SN field, and an SO field. In an RLC UM mode in which an ARQis not supported, the P field is not included, but may be replaced by areservation field.

The D/C field is composed of 1 bit, and is used to indicate whether theconfigured RLC PDU is a control PDU or a data PDU.

TABLE 1 Value Description 0 Control PDU 1 Data PDU

The SN field indicates a serial number of the RLC PDU, and may have aspecific length. For example, the SN field may have a length of 12 bitsor 18 bits.

The SO field is used to indicate at what location on the original RLCSDU the RLC SDU segment is segmented and to indicate the first segmentedbyte. The P field may be set to 1 if a polling triggering conditionoccurs in a transmitting end to make a receiving end perform an RLCstatus report. That is, the P field makes it possible to transferACK/NACK information for the RLC PDUs received up to now to thetransmitting end.

If the RLC layer receives the RLC SDU at 1 f-05, it may directly insertan RLC SN into the RLC SDU, and generate an RLC header to make the RLCPDU. If segmentation is necessary for a specific reason, the RLC layermay update the SI field at 1 f-10 or 1 f-15, and add the SO field to theRLC header to generate the RLC PDU. That is, the SO field may or may notbe added to the segmented segment in accordance with a specificcondition after the segmentation operation. The specific condition isdetermined in accordance with the SI field. The segmentation operationis necessary when the size of the transmission resource allocated by theMAC layer is greater than the size of the MAC sub-header and the MAC SDUcurrently generated, and thus the RLC layer is requested to perform thesegmentation operation with respect to a specific MAC SDU (RLC PDU).

The SN field is a serial number of the RLC PDU, and if it is necessaryor it is set, the PDCP SN may be reused. The SO field is a field havinga specific length, and may indicate what byte of the original RLC PDUdata field (RLC SDU) the first byte of the RLC PDU data field (RLC SDU)segmented during an initial transmission corresponds to, and during theretransmission, it may indicate what byte of the original RLC PDU datafield (RLC SDU) the first byte of the re-segmented RLC PDU data fieldcorresponds to.

The length of the SO field may be set by an RRC message (e.g.,RRCConnectionSetup or RRCConnectionReconfiguration message at steps 1e-10, 1 e-40, or 1 e-75). For example, the length of the SO field or thekind of settable SO fields (short SO or long SO) may be differently setfor each bearer. That is, in a VoLTE or VoIP service, the SO field canbe set to 1 byte, whereas in an eMBB service, the SO field can be set to2 bytes. Further, a specific bit may be defined in front of the SO fieldso that the specific bit can indicate the length of the SO field. Forexample, if it is assumed that the specific bit is 1 bit, 0 may indicatethat the SO field has the length of 1 byte, whereas 1 may indicate thatthe SO field has the length of 2 bytes. As described above, the SI fieldmay be defined as follows using the values of Table 2 below.

TABLE 2 Value Description 00 A complete RLC PDU 01 First segment of aRLC PDU 10 Last segment of a RLC PDU 11 Middle segment of a RLC PDU

If the SI field is 00, it represents a complete RLC PDU that is notsegmented, and in this case, the RLC header does not require the SOfield. If the SI field is 01, it represents the foremost RLC PDU segmentthat is segmented, and in this case, the RLC header does not require theSO field. This is because the SO field always indicates 0 in case of thefirst segment. If the SI field is 10, it represents the last RLC PDUsegment that is segmented, and in this case, the RLC header requires theSO field. If the SI field is 11, it represents the middle RLC PDUsegment that is segmented, and in this case, the RLC header requires theSO field. The number of mapping relations between the 2 bits and thefour kinds of information (complete RLC PDU, foremost segment, lastsegment, and middle segment) is 24 (=4×3×2×1) in total; all 24 kinds ofmappings are included.

If transmission of the RLC PDUs at 1 f-10 and 1 f-15 has failed,retransmission may be performed, and in this case, if the transmissionresource is insufficient, re-segmentation, at 1 f-20, 1 f-25, and 1f-30, may be performed. During the re-segmentation, SI fields and SOfields of newly generated RLC PDUs at 1 f-20, 1 f-25, and 1 f-30 may beupdated. With respect to 1 f-20 that is the foremost segment, the SI isupdated to 01, and the SO field is not necessary.

For example, at 1 f-25, which is the middle segment, the SI is updatedto 11, and the SO field is updated to 300 to indicate what byte of theoriginal RLC PDU data field (RLC SDU) the first byte of the RLC PDU datafield (RLC SDU) corresponds to. At 1 f-30, which is the last segment,the SI is updated to 10, and the SO field is updated to 600 to indicatewhat byte of the original RLC PDU data field (RLC SDU) the first byte ofthe RLC PDU data field (RLC SDU) corresponds to.

FIGS. 1GA and 1GB are diagrams of an RLC header, according to anembodiment.

FIG. 1GA illustrates an RLC header structure using an RLC AM mode(supporting an ARQ), and at 1 g-11 an RLC header structure using aserial number having a length of 12 bits in a segmentation operationbased on the SO field and SI field is shown. The RLC header structuremay include parts of the fields as described above with reference toFIG. 1F or other new fields, and may have a different structure inaccordance with lengths of the respective fields, such as different RLCserial number lengths or SO field lengths, and locations of therespective fields.

R is a reserved bit, and a P field is a field for requesting a statusreport from a corresponding RLC entity of a receiving end. For example,if the P field is 0, the status report is not requested, whereas if theP field is 1, the status report is requested. The status report mayinclude information on data received up to now. The RLC header structureis featured not to have a re-segmentation flag (RF) field, a framinginfo (FI) field, or an extension bit (E) field. Further, the RLC headerstructure is featured to use an integrated header without dividing theRLC header into those in case of an initial transmission and aretransmission. As described above, the SI field serves to indicate theRLC SDU that has not been segmented, and the first, middle, and lastsegments that have been segmented as described above with reference toFIG. 1F. As described above with reference to FIG. 1F, since the SOfield is not necessary with respect to the RLC SDU that has not beensegmented and the first segment that has been segmented, the RLC headermay be used in the format of 1 g-11. However, since the SO field shouldindicate the offset with respect to the middle and last segments thathave been segmented, the RLC header format of 1 g-12 may be used.

When using an RLC AM mode (when supporting an ARQ) in FIG. 1GA, 1 g-21indicates an RLC header format using an RLC serial number having alength of 18 bits; this format can be applied to the RLC SDU that hasnot been segmented and the first segment that has been segmented.Further, the format of 1 g-22 is a format that can be applied to themiddle and last segments generated through performing of thesegmentation operation, since the SO field should indicate an offset.

When using an RLC UM mode (when supporting no ARQ) in FIG. 1GB, 1 g-31indicates an RLC header format using an RLC serial number having alength of 12 bits; this format can be applied to the RLC SDU that hasnot been segmented and the first segment that has been segmented.Further, the format of 1 g-32 can be applied to the middle and lastsegments generated through performing of the segmentation operation,since the SO field should indicate an offset. When indicating an offsetby the SO field having a relatively long length, the format of 1 g-33may be applied. Whether to use the SO field having a short length or theSO field having a long length can be determined at a terminal at steps 1e-10, 1 e-40, and 1 e-75 when a base station configures the terminal inaccordance with the method of FIG. 1E.

Further, the terminal may be configured not to use the RLC serial numberin the RLC UM mode at steps 1 e.10, 1 e-40, and 1 e-75. The terminal isconfigured not to use the RLC serial number in the RLC UM mode to reducean overhead, and since the RLC ARQ function is not necessary in the RLCUM mode, the operation can be performed even without the RLC serialnumber.

When it is determined not to use an RLC serial number, a transmittingend may not attach an RLC header (1-bit indicator may be included at thehead in order to indicate whether the segmentation operation has beenperformed) to an RLC SDU that has not been segmented, and may transferthe RLC SDU to a lower layer to perform the transmission. However, ifthe RLC SDU has been segmented even in case of the configuration not touse the RLC serial number to reduce the overhead, the RLC serial numbershould be added, and the SI field and the SO field as described abovewith reference to FIG. 1F should be used. The r RLC header is configuredby applying the RLC serial number, the SI field, and the SO field withrespect to the segmented RLC SDU so that a receiving end can receive andreassemble the segmented RLC SDU segments to restore to a complete RLCSDU. Accordingly, if the segmentation operation has been performed, evenin case of the configuration not to use the RLC serial number in the RLCUM mode, the RLC header, e.g., 1 g-31, 1 g-32, or 1 g-33, should beapplied. That is, the first segment may use the format of 1 g-31, andthe middle segments and the last segment may use the format of 1 g-32 or1 g-33.

Depending on whether the segmentation of the RLC SDU has been performed,the transmitting end may not attach the header (1-bit indicator may beincluded at the head in order to indicate whether the segmentationoperation has been performed) to the RLC SDU that has not beensegmented, and may transmit the RLC SDU to the lower layer. In contrast,with respect to the RLC SDU that has been segmented, as described above,the transmitting end may update the corresponding SI field in accordancewith the kind/type (first, middle, or last) of the segmented segment,configure the RLC header by adding the SO field to the middle and thelast segments, and transfer the RLC SDU to the lower layer.

The receiving end may receive the RLC SDU, identify the foremost 1-bitindicator, and discriminate whether the received RLC SDU is the RLC SDUthat has not been segmented (complete RLC SDU) or the RLC SDU that hasbeen segmented (segment). If the RLC SDU has not been segmented, thereceiving end may discard the 1-bit indicator and may send the RLC SDUto an upper layer. If the RLC SDU has been segmented, the receiving endmay identify whether the RLC SDU is the first, middle, or last segmentbased on the SI field, arrange the segments to match the RLC serialnumbers in consideration of the SO field or the like, and if areassembly function is triggered by a window or a timer, it may make acomplete RLC SDU through reassembly of the segments to transfer thecomplete RLC SDU to the upper layer. In contrast, if the reassembly ofthe segments is not possible, the RLC SDU is discarded.

In the RLC UM mode, the receiving end may operate based on the window orthe timer.

When the operation is based on the window, the receiving end may operatean RLC reception window, and the window may be operated with a sizecorresponding to a half of the RLC serial number. With respect to alower edge of the window, a serial number through subtraction of thesize of the RLC window from an upper edge may be configured, and thehighest RLC serial number received from the receiving end RLC may beconfigured at the upper edge. Accordingly, if the received RLC serialnumber has a larger value than the values of the RLC serial numbers inthe window, the window moves accordingly. If the received RLC PDU serialnumber has a smaller value than the value of the received window loweredge, the receiving end RLC layer may discard this RLC PDU serialnumber, and may check whether a duplicate RLC PDU is received withrespect to the RLC serial number existing in the window to discard thesame.

Further, if an RLC PDU segment having an RLC serial number existing inthe window arrives, the receiving end RLC layer may store this, and ifthe lower edge of the window passes the RLC serial number correspondingto the RLC PDU segment, the receiving end RLC layer may generate andsend a complete RLC PDU through performing of a reassembling procedure,whereas if the complete RLC PDU is unable to be generated, the receivingend RLC layer may discard the RLC PDU segments. Further, the receivingend RLC layer may identify the SI field or 1-bit indicator (indicatorindicating whether the segmentation has been performed), and maydirectly send the RLC PDU that has not been segmented to the upperlayer. Further, if the SI field or the 1-bit indicator indicates the RLCPDU that has been segmented, the receiving end RLC layer stores the RLCPDU segments, and if the reassembling procedure is triggered by thewindow as described above, the receiving end RLC layer performs thereassembling procedure to send the reassembled RLC PDU to the upperlayer or to discard the same.

When the operation is based on the timer, the receiving end RLC layeroperates the timer in the RLC UM mode. The receiving end RLC layer mayoperate several timers or one timer.

When operating only one timer, the receiving end RLC layer identifiesthe SI field or 1-bit indicator, and directly sends the RLC PDU that hasnot been segmented to the upper layer. If the SI field or the 1-bitindicator indicates the RLC PDU that has been segmented, the receivingend RLC layer stores the RLC PDU segments, and operates the timer. Thatis, timer triggering is performed when the segmented RLC PDU segmentarrives.

Thereafter, if the RLC PDUs are received, the above-described process isrepeated, and if the RLC PDU segment arrives again, the receiving endRLC layer identifies whether the timer is operated, and if the timer isnot operated, the receiving end RLC layer restarts the timer. If thetimer expires, the receiving end RLC layer reassembles the RLC PDUsegments received up to now, and sends the reassembly-completed completeRLC PDUs to the upper layer while discarding the reassembly-failed RLCPDU segments.

When operating several timers, the receiving end RLC layer identifiesthe SI field or 1-bit indicator, and directly sends the RLC PDU that hasnot been segmented to the upper layer. If the SI field or the 1-bitindicator indicates the RLC PDU that has been segmented, the receivingend RLC layer stores the RLC PDU segments, and operates the timer withrespect to the RLC serial numbers of the RLC PDU segments. That is,timer triggering is performed when the segmented RLC PDU segmentcorresponding to a specific RLC serial number arrives.

Thereafter, if the RLC PDUs are received, the above-described process isrepeated, and if the RLC PDU segment arrives again, the receiving endRLC layer identifies whether the timer corresponding to the RLC serialnumber of the received RLC PDU segment is operated, and if the timer isnot operated, the receiving end RLC layer restarts the timer. If thetimer corresponding to the RLC serial number is not operated, thereceiving end RLC layer may operate a new timer with respect to thecorresponding RLC serial number. Accordingly, whenever the RLC PDUsegment arrives for each RLC serial number, the timer can be operatedfor each RLC serial number. If the timer for the specific RLC serialnumber expires, the receiving end RLC layer reassembles the RLC PDUsegments having the RLC serial numbers corresponding to the timerreceived up to now, and sends the reassembly-completed complete RLC PDUsto the upper layer while discarding the reassembly-failed RLC PDUsegments.

When not using an RLC serial number, the transmitting end may attach a1-byte RLC header, such as 1 g-31-1, having no RLC serial number (whenconfiguring the RLC header, the SI field is set to 00, and the RLCheader to which the SO field is not added) with respect to the RLC SDUthat has not been segmented, and may transfer the RLC SDU to the lowerlayer to perform the transmission. However, if the RLC SDU has beensegmented, even when not using the RLC serial number to reduce theoverhead, the RLC serial number should be added, and the SI field andthe SO field as described above with reference to FIG. IF should beused. The RLC header is configured by applying the RLC serial number,the SI field, and the SO field with respect to the segmented RLC SDU sothat a receiving end can receive and reassemble the segmented RLC SDUsegments to restore to a complete RLC SDU. Accordingly, if thesegmentation operation has been performed even when not using the RLCserial number in the RLC UM mode, the RLC header, e.g., 1 g-31, 1 g-32,or 1 g-33, should be applied. That is, the first segment may use theformat of 1 g-31, and the middle segments and the last segment may usethe format of 1 g-32 or 1 g-33.

Depending on whether the segmentation of the RLC SDU has been performed,the transmitting end may attach the 1-byte RLC header, such as 1 g-31-1,having no RLC serial number with respect to the RLC SDU that has notbeen segmented, and may transmit the RLC SDU to the lower layer. Incontrast, with respect to the RLC SDU that has been segmented, asdescribed above, the transmitting end may update the corresponding SIfield in accordance with the kind/type (first, middle, or last) of thesegmented segment, configure the RLC header by adding the SO field tothe middle and the last segments, and transfer the RLC SDU to the lowerlayer.

The receiving end may receive the RLC SDU, identify the SI field fromthe RLC header, and discriminate whether the received RLC SDU is the RLCSDU that has not been segmented (complete RLC SDU) or the RLC SDU thathas been segmented (segment). If the RLC SDU has not been segmented, thereceiving end may discard the RLC header and may send the RLC SDU to theupper layer. If the RLC SDU has been segmented, the receiving end mayidentify whether the RLC SDU is the first, middle, or last segment basedon the SI field, arrange the segments to match the RLC serial numbers inconsideration of the SO field or the like, and if the reassemblyfunction is triggered by a window or a timer, it may make the completeRLC SDU through reassembly of the segments to transfer the complete RLCSDU to the upper layer. If the reassembly of the segments is notpossible, the RLC SDU is discarded.

In the RLC UM mode, the receiving end may operate based on the window orthe timer.

When the operation based on the window, the receiving end may operate anRLC reception window, and the window may be operated with a sizecorresponding to a half of the RLC serial number. When a lower edge ofthe window, a serial number through subtraction of the size of the RLCwindow from an upper edge may be used, and the highest RLC serial numberreceived from the receiving end RLC may be used at the upper edge.Accordingly, if the received RLC serial number has a larger value thanthe values of the RLC serial numbers in the window, the window movesaccordingly. If the received RLC PDU serial number has a smaller valuethan the value of the received window lower edge, the receiving end RLClayer may discard this RLC PDU serial number, and may check whether aduplicate RLC PDU is received with respect to the RLC serial numberexisting in the window to discard the same.

Further, if an RLC PDU segment having an RLC serial number existing inthe window arrives, the receiving end RLC layer may store this RLCserial number, and if the lower edge of the window passes the RLC serialnumber corresponding to the RLC PDU segment, the receiving end RLC layermay generate and send a complete RLC PDU through performing of areassembling procedure. If the complete RLC PDU is unable to begenerated, the receiving end RLC layer may discard the RLC PDU segments.Further, the receiving end RLC layer may identify the SI field or 1-bitindicator, and may directly send the RLC PDU that has not been segmentedto the upper layer. Further, if the SI field or the 1-bit indicatorindicates the RLC PDU that has been segmented, the receiving end RLClayer stores the RLC PDU segments, and if the reassembling procedure istriggered by the window as described above, the receiving end RLC layerperforms the reassembling procedure to send the reassembled RLC PDU tothe upper layer or to discard the same.

When the operation is based on the timer, the receiving end RLC layeroperates the timer in the RLC UM mode. The receiving end RLC layer mayoperate several timers or one timer.

When operating only one timer, the receiving end RLC layer identifiesthe SI field or 1-bit indicator, and directly sends the RLC PDU that hasnot been segmented to the upper layer. If the SI field or the 1-bitindicator indicates the RLC PDU that has been segmented, the receivingend RLC layer stores the RLC PDU segments, and operates the timer. Thatis, timer triggering is performed when the segmented RLC PDU segmentarrives.

Thereafter, if the RLC PDUs are received, the above-described process isrepeated, and if the RLC PDU segment arrives again, the receiving endRLC layer identifies whether the timer is operated, and if the timer isnot operated, the receiving end RLC layer restarts the timer. If thetimer expires, the receiving end RLC layer reassembles the RLC PDUsegments received up to now, and sends the reassembly-completed completeRLC PDUs to the upper layer while discarding the reassembly-failed RLCPDU segments.

When operating several timers, the receiving end RLC layer identifiesthe SI field or 1-bit indicator, and directly sends the RLC PDU that hasnot been segmented to the upper layer. If the SI field or the 1-bitindicator indicates the RLC PDU that has been segmented, the receivingend RLC layer stores the RLC PDU segments, and operates the timer withrespect to the RLC serial numbers of the RLC PDU segments. That is,timer triggering is performed when the segmented RLC PDU segmentcorresponding to a specific RLC serial number arrives.

Thereafter, if the RLC PDUs are received, the above-described process isrepeated, and if the RLC PDU segment arrives again, the receiving endRLC layer identifies whether the timer corresponding to the RLC serialnumber of the received RLC PDU segment is operated, and if the timer isnot operated, the receiving end RLC layer restarts the timer. If thetimer corresponding to the RLC serial number is not operated, thereceiving end RLC layer may operate a new timer with respect to thecorresponding RLC serial number. Accordingly, whenever the RLC PDUsegment arrives for each RLC serial number, the timer can be operatedfor each RLC serial number. If the timer for the specific RLC serialnumber expires, the receiving end RLC layer reassembles the RLC PDUsegments having the RLC serial numbers corresponding to the timerreceived up to now, and sends the reassembly-completed complete RLC PDUsto the upper layer while discarding the reassembly-failed RLC PDUsegments.

FIGS. 1HA and 1HB are diagrams of a method in which a terminalconfigures an RLC header, according to an embodiment.

In an RLC AM mode (at step 1 h-01), if a segmentation operation isrequested from a lower layer with respect to an RLC SDU (PDCP PDU)transferred from an upper layer, a terminal may perform the segmentationoperation. Further, if a segmentation request comes from the lowerlayer, even when the RLC header has already been configured and the RLCPDU has been sent to the lower layer, the terminal may perform thesegmentation operation, and may newly configure or update the RLC headerto transfer the RLC PDU again to the lower layer. As described above,when configuring the RLC header for the RLC SDU, the terminal firstidentifies whether the segmentation operation is necessary (1 h-10).

If a first condition is satisfied, the terminal performs a firstoperation (at step 1 h-15),

if a second condition is satisfied, the terminal performs a secondoperation (at step 1 h-20),

if a third condition is satisfied, the terminal performs a thirdoperation (at step 1 h-25), and

if a fourth condition is satisfied, the terminal performs a fourthoperation (at step 1 h-30).

The first condition corresponds to a case when the segmentationoperation is not necessary with respect to the RLC SDU, and thesegmentation operation is not performed, and the RLC header for acomplete RLC SDU should be configured.

The second condition corresponds to a case when the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the first RLC SDU segment.

The third condition corresponds to a case when the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the middle RLC SDU segment that is not the first or lastRLC SDU segment.

The fourth condition corresponds to a case when the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the last RLC SDU segment.

For example, the first operation may include setting the SI field to 00when configuring the RLC header and configuring the RLC header to whichthe SO field is not added.

The second operation may include setting the SI field to 01 whenconfiguring the RLC header and configuring the RLC header to which theSO field is not added.

The third operation may include setting the SI field to 11 whenconfiguring the RLC header and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

The fourth operation may include setting the SI field to 10 whenconfiguring the RLC header and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

In an RLC UM mode (at step 1 h-50), a segmentation operation isrequested from a lower layer with respect to an RLC SDU (PDCP PDU)transferred from an upper layer, and a terminal may perform thesegmentation operation. Further, if a segmentation request comes fromthe lower layer, even when the RLC header has already been configuredand the RLC PDU has been sent to the lower layer, the terminal mayperform the segmentation operation, and may newly configure or updatethe RLC header to transfer the RLC PDU again to the lower layer. Asdescribed above, when configuring the RLC header for the RLC SDU, theterminal first identifies whether the segmentation operation isnecessary (at step 1 h-55).

If a first condition is satisfied, the terminal performs a firstoperation (1 h-60),

if a second condition is satisfied, the terminal performs a secondoperation (at step 1 h-65),

if a third condition is satisfied, the terminal performs a thirdoperation (at step 1 h-70), and

if a fourth condition is satisfied, the terminal performs a fourthoperation (at step 1 h-75).

The first condition corresponds to a case when the segmentationoperation is not necessary with respect to the RLC SDU, and thus thesegmentation operation is not performed. The second conditioncorresponds to a case when the segmentation operation is necessary withrespect to the RLC SDU, and the segmentation operation is performed, andthen the RLC header should be configured with respect to the first RLCSDU segment.

The third condition corresponds to a case when the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the middle RLC SDU segment that is not the first or lastRLC SDU segment.

The fourth condition corresponds to a case where since the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the last RLC SDU segment.

The first operation may include not configuring the RLC header if thebase station configures the terminal not to use the RLC serial number inorder to reduce the overhead. If the base station does not configure theabove-described indication, the first operation may include operationsof setting the SI field to 00 when configuring the RLC header andconfiguring the RLC header to which the SO field is not added.

The second operation may include setting the SI field to 01 whenconfiguring the RLC header and configuring the RLC header to which theSO field is not added.

The third operation may include setting the SI field to 11 whenconfiguring the RLC header and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

The fourth operation may include setting the SI field to 10 whenconfiguring the RLC header and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

Alternatively, the disclosure provides a procedure and a method in whichan RLC layer performs SO-based segmentation operations with respect topackets received from an upper layer. In this procedure an integratedsegmentation operation, without dividing the segmentation operation,during an initial transmission and a retransmission. The RLC layer doesnot perform concatenation. Further, an SI field can be introduced intoan RLC header to discriminate whether an RLC SDU that is a data part inthe rear of the RLC header is a complete RLC SDU that has not beensegmented, the foremost segmented RLC SDU segment, a middle segmentedRLC SDU segment, or the last segmented RLC SDU segment. When an SO fieldis added to the middle segment and the last segment among the segmentedRLC SDU segments, it may be selected whether to use the SO field havinga short length or the SO field having a long length in consideration ofthe length that can be indicated by the SO field.

A method capable of further reducing the overhead through selection ofwhether to use a short SO field or a long SO field is provided; thismethod takes into account a length that can be indicated by the SO fieldwhen the SO field is added to the middle segment and the last segmentamong the segmented RLC SDU segments in addition to all the sameoperations as those of the (1-1)-th embodiment.

An SO length type (ST) field may be added. The ST field (SO length typefield=ST field) is a field indicating selection of whether to use theshort SO field or the long SO field in consideration of the length thatcan be indicated by the SO field when the SO field is added to themiddle segment and the last segment among the segmented RLC SDUsegments. For example, the SO field may have the short length of 7 or 8bits, and the long length of 15 or 16 bits.

TABLE 3 Value Description 0 Short SO field 1 Long SO field

That is, the short SO and the long SO are defined, and the SO lengthtype (ST) field is introduced into the RLC PDU header to indicate theshort SO/long SO through in-band signaling. For example, if the RLC SDUis segmented into SDU segment 0, segment 1, . . . , segment n, the SOfield lengths for the respective segments may differ from each other.For example, seg 0 may be applied as no SO, seg 1 to seg m may beapplied as short SO, and seg m+1 to seg n may be applied as long SO.

When using the short SO and the long SO as described above, thereceiving end should convert the received short SO into the long SO toread and apply the converted long SO through attachment of 0000 . . . tothe front part of the short SO during reassembling. If it is assumedthat the short SO is of 8 bits and the long SO is of 16 bits, thereceiving end, even if the short SO of 0000 0100 is received, mayanalyze the received short SO as the long SO of 0000 0000 0000 0100through attachment of 0000 0000 to the front part of the short SO of0000 0100.

As described above, during the RLC SDU segment transmission, one of theshort SO and the long SO is selectively used, whereas if the receivingend requests the RLC SDU segment retransmission, only the long SO isused. That is, one of the short SO and the long SO is selectively usedin the RLC PDU header, and only the long SO is used for an RLC STATUSPDU RLC (status report) transmitted from the receiving end to thetransmitting end. Even if the short SO is used during certain RLC SDUsegment transmission, the long SO is used when retransmission of thecorresponding RLC SDU segment is requested. In other words, when the RLCSDU is segmented into several segments to be transmitted, even if theshort SO is applied during transmission of certain bytes belonging tothe corresponding SDU, the long SO is applied when retransmission of thesame bytes is requested.

During a terminal transmission operation in an uplink throughsegmentation and transmission of a certain SDU, if a distance between afirst byte of a data field of the segmented and transmitted middlesegment and last segment and a first byte of the original SDU data fieldor a first byte of a data field of the previous segment is less than orequal to specific n bytes, the short SO is used, whereas if the distanceis greater than the n bytes, the long SO is used. The SI field mayindicate the middle segment or the last segment, and the ST field may beset to 0 or 1. The specific n bytes may be determined as the length ofthe short SO. For example, the specific n bytes may be set ton=2^({circumflex over ( )}(length of short SO)−1).

During a terminal reception operation in a downlink, if the SI fieldindicates the existence of the SO, the short SO or the long SO may beanalyzed based on the SO-length type field (ST field), and segmentreassembly is performed to configure a complete RLC SDU.

Further, when the base station configures the terminal as illustrated inFIG. 1E, whether to use the short SO field or the long SO field for eachbearer may be determined through an RRC message of at steps 1 e-10, 1e-40, and 1 e-75 of FIG. 1E. For example, only the long SO can be usedat a high data rate, and the short SO field and the long SO field aremixedly used only for VoIP or VoLTE services.

FIGS. 1IA and 1IB are diagrams of an RLC header, according to anembodiment.

FIG. 1IA illustrates an RLC header structure when of using an RLC AMmode (when supporting an ARQ). 1 i-11 illustrates an RLC headerstructure f when using a serial number having a length of 12 bits in asegmentation operation based on the SO field and SI field as describedabove with reference to FIG. 1F. The RLC header structure may includeparts of the fields as described above with reference to FIG. 1F orother new fields, and may have a different structure in accordance withlengths of the respective fields, such as different RLC serial numberlengths or SO field lengths, and locations of the respective fields.

R is a reserved bit, and a P field is a field for requesting a statusreport from a corresponding RLC entity of a receiving end. If the Pfield is 0, the status report is not requested, whereas if the P fieldis 1, the status report is requested. The status report may includeinformation on data received up to now. The RLC header structure doesnot to have an RF field, an FI field, or an E field. Further, the RLCheader structure is featured to use an integrated header withoutdividing the RLC header into those in case of an initial transmissionand a retransmission. As described above, the SI field serves toindicate the RLC SDU that has not been segmented, and the first, middle,and last segments that have been segmented as described above withreference to FIG. 1F. As described above with reference to FIG. 1F,since the SO field is not necessary with respect to the RLC SDU that hasnot been segmented and the first segment that has been segmented, theRLC header may be used in the format of 1 i-11.

However, since the SO field should indicate the offset with respect tothe middle and last segments that have been segmented, the RLC headerformat of 1 i-12 may be used. During a terminal transmission operationin an uplink through segmentation and transmission of certain SDU, if adistance between a first byte of a data field of the segmented andtransmitted middle segment and last segment and a first byte of theoriginal SDU data field or a first byte of a data field of the previoussegment is less than or equal to specific n bytes, the short SO is used.Conversely, if the distance is larger than the n bytes, the long SO isused. The SI field may indicate the middle segment or the last segment,and the ST field may be set to 0 (short SO indication) or 1 (long SOindication). Accordingly, the format of 1 i-12 or 1 i-13 may be used.The specific n bytes may be determined as the length of the short SO.For example, the specific n bytes may be set ton=2^({circumflex over ( )}(length of short SO)−1). During a terminalreception operation in a downlink, if the SI field indicates theexistence of the SO, the short SO or the long SO may be analyzed basedon the SO-length type field (ST field), and segment reassembly isperformed to configure a complete RLC SDU.

When using an RLC AM mode (when supporting an ARQ) in FIG. 1IA, 1 i-21is an RLC header format using an RLC serial number having a length of 18bits, and this format can be applied to the RLC SDU that has not beensegmented and the first segment that has been segmented. Further, theformat of 1 i-22 is a format that can be applied to the middle and lastsegments generated through performing of the segmentation operationsince the SO field should indicate an offset.

During the terminal transmission operation in an uplink throughsegmentation and transmission of certain SDU, if a distance between afirst byte of a data field of the segmented and transmitted middlesegment and last segment and a first byte of the original SDU data fieldor a first byte of a data field of the previous segment is less than orequal to specific n bytes, the short SO is used. Conversely, if thedistance is larger than the n bytes, the long SO is used. The SI fieldmay indicate the middle segment or the last segment, and the ST fieldmay be set to 0 (short SO indication) or 1 (long SO indication).Accordingly, the format of 1 i-22 or 1 i-23 may be used. The specific nbytes may be determined as the length of the short SO. For example, thespecific n bytes may be set ton=2^({circumflex over ( )}(length of short SO)−1). During the terminalreception operation in a downlink, if the SI field indicates theexistence of the SO, the short SO or the long SO may be analyzed basedon the SO-length type field (ST field), and segment reassembly isperformed to configure a complete RLC SDU. Further, whether it ispossible to selectively use the short SO field or the long SO field foreach bearer may be determined by the terminal at steps 1 e-10, 1 e-40,and 1 e-75 in FIG. 1E when the base station configures the terminal inaccordance with the method of FIG. 1E. If the terminal is notconfigured, the format as illustrated in FIG. 1GA may be applied.

When using an RLC UM mode (when supporting no ARQ) in FIG. 1IB, 1 i-31is an RLC header format using an RLC serial number having a length of 12bits, and this format can be applied to the RLC SDU that has not beensegmented and the first segment that has been segmented. Further, theformats of 1 i-32 and 1 i-33 can be applied to the middle and lastsegments generated through the segmentation operation since the SO fieldshould indicate an offset.

During the terminal transmission operation in an uplink throughsegmentation and transmission of certain SDU, if a distance between afirst byte of a data field of the segmented and transmitted middlesegment and last segment and a first byte of the original SDU data fieldor a first byte of a data field of the previous segment is less than orequal to specific n bytes, the short SO is used. Conversely, if thedistance is greater than the n bytes, the long SO is used. The SI fieldmay indicate the middle segment or the last segment, and the ST fieldmay be set to 0 (short SO indication) or 1 (long SO indication).Accordingly, the format of 1 i-22 or 1 i-23 may be used. The specific nbytes may be determined as the length of the short SO. For example, thespecific n bytes may be set ton=2^({circumflex over ( )}(length of short SO)−1). During the terminalreception operation in a downlink, if the SI field indicates theexistence of the SO, the short SO or the long SO may be analyzed basedon the SO-length type field (ST field), and segment reassembly isperformed to configure a complete RLC SDU. When indicating the offset bythe short SO field, the format of 1 i-32 may be applied, whereas in caseof indicating the offset by the long SO field, the format of 1 i-33 maybe applied. Further, whether it is possible to selectively use the shortSO field or the long SO field for each bearer may be determined by theterminal at steps 1 e-10, 1 e-40, and 1 e-75 of FIG. 1E when the basestation configures the terminal in accordance with FIG. 1E. If theterminal is not configured in such a manner, the format as illustratedin FIG. 1GB may be applied.

On the other hand, the terminal may be configured not to use the RLCserial number in the RLC UM mode at steps 1 e.10, 1 e-40, and 1 e-75when the base station configures the terminal in accordance with FIG.1E. The terminal is configured not to use the RLC serial number in theRLC UM mode to reduce an overhead, and since the RLC ARQ function is notnecessary in the RLC UM mode, the operation can be performed evenwithout the RLC serial number. That is, when the RLC serial number isnot used, an RLC header is not attached to an RLC SDU that has not beensegmented, and the RLC SDU may be transmitted to a lower layer. Further,1-byte RLC header such as 1 i-31-1 may be attached to the RLC SDU to betransmitted to the lower layer. However, if the RLC SDU has beensegmented, even when the RLC serial number is not used to reduce theoverhead, the RLC serial number should be added, and the SI field andthe SO field as described above with reference to FIG. 1F should beused. The RLC header is configured by applying the RLC serial number,the SI field, and the SO field with respect to the segmented RLC SDU sothat the receiving end can receive and reassemble the segmented RLC SDUsegments to restore to a complete RLC SDU. Accordingly, if thesegmentation operation has been performed, even in case of theconfiguration not to use the RLC serial number in the RLC UM mode, theRLC header, e.g., 1 i-31, 1 i-32, or 1 i-33, should be applied inaccordance with the SO field length. That is, the first segment may usethe format of 1 i-31, and the middle segments and the last segment mayuse the format of 1 i-32 or 1 i-33.

FIGS. 1JA and 1JB are flowcharts of a method in which a terminalconfigures an RLC header, according to an embodiment.

In an RLC AM mode (at step 1 j-01), if it is necessary to perform asegmentation operation requested from a lower layer with respect to anRLC SDU (PDCP PDU) transferred from an upper layer, a terminal mayperform the segmentation operation. Further, if a segmentation requestcomes from the lower layer, even in case where the RLC header hasalready been configured and the RLC PDU has been sent to the lowerlayer, the terminal may perform the segmentation operation, and maynewly configure or update the RLC header to transfer the RLC PDU againto the lower layer. As described above, when configuring the RLC headerfor the RLC SDU, the terminal first identifies whether the segmentationoperation is necessary (at step 1 j-10).

If a first condition is satisfied, the terminal performs a firstoperation (at step 1 j-15),

if a second condition is satisfied, the terminal performs a secondoperation (at step 1 j-20),

if a third condition and a fourth condition are satisfied, the terminalperforms a third operation (at steps 1 j-25 and 1 j-30), and

if the third condition and a fifth condition are satisfied, the terminalperforms a fourth operation (at steps 1 j-25 and 1 j-35).

The first condition corresponds to a case when the segmentationoperation is not necessary with respect to the RLC SDU, and thesegmentation operation is not performed, and the RLC header for acomplete RLC SDU should be configured.

The second condition corresponds to a case when the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the first RLC SDU segment.

The third condition corresponds to a case when the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the middle and last RLC SDU segments that are not thefirst RLC SDU segment.

The fourth condition corresponds to a case when the short SO field isused since a distance between a first byte of a data field of thesegmented and transmitted middle segment and last segment and a firstbyte of the original SDU data field or a first byte of a data field ofthe previous segment is less than or equal to specific n bytes duringthe SDU segmentation and transmission.

The fifth condition corresponds to a case when the long SO field is usedsince the distance between the first byte of the data field of thesegmented and transmitted middle segment and last segment and the firstbyte of the original SDU data field or the first byte of the data fieldof the previous segment exceeds the specific n bytes during the SDUsegmentation and transmission.

The first operation may include setting the SI field to 00 whenconfiguring the RLC header and configuring the RLC header to which theSO field is not added.

The second operation may include setting the SI field to 01 whenconfiguring the RLC header and configuring the RLC header to which theSO field is not added.

The third operation may include setting the SI field to 11 whenconfiguring the RLC header, setting the ST field to 0 to indicate theuse of the short SO field, and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

The fourth operation may include setting the SI field to 10 whenconfiguring the RLC header, setting the ST field to 1 to indicate theuse of the long SO field, and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

Accordingly, the receiving end can identify the SI field, the kind ofsegment, and then existence/nonexistence of the SO field. If theexistence of the SO field is identified through the SI field, it isdetermined whether the SO field is the short SO or the long SO throughthe ST field to perform the reception processing.

In an RLC UM mode (at step 1 j-50), if a necessity to perform asegmentation operation is requested from a lower layer with respect toan RLC SDU (PDCP PDU) transferred from an upper layer, a terminal mayperform the segmentation operation. Further, if a segmentation requestcomes from the lower layer even in case when the RLC header has alreadybeen configured and the RLC PDU has been sent to the lower layer, theterminal may perform the segmentation operation, and may newly configureor update the RLC header to transfer the RLC PDU again to the lowerlayer. As described above, when configuring the RLC header for the RLCSDU, the terminal first identifies whether the segmentation operation isnecessary (at step 1 j-55).

If a first condition is satisfied, the terminal performs a firstoperation (at step 1 j-60),

if a second condition is satisfied, the terminal performs a secondoperation (at step 1 j-65),

if a third condition and a fourth condition are satisfied, the terminalperforms a third operation (at steps 1 j-70 and 1 j-75), and

if the third condition and a fifth condition are satisfied, the terminalperforms a fourth operation (at steps 1 j-70 and 1 j-80).

The first condition corresponds to a case when the segmentationoperation is not necessary with respect to the RLC SDU, and thus thesegmentation operation is not performed.

The second condition corresponds to a case when since the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the first RLC SDU segment.

The third condition corresponds to a case when since the segmentationoperation is necessary with respect to the RLC SDU, and the segmentationoperation is performed, and then the RLC header should be configuredwith respect to the middle and last RLC SDU segments that are not thefirst segment.

The fourth condition corresponds to a case when the short SO field isused since a distance between a first byte of a data field of thesegmented and transmitted middle segment and last segment and a firstbyte of the original SDU data field or a first byte of a data field ofthe previous segment is less than or equal to specific n bytes duringthe SDU segmentation and transmission.

The fifth condition corresponds to a case when the long SO field is usedsince the distance between the first byte of the data field of thesegmented and transmitted middle segment and last segment and the firstbyte of the original SDU data field or the first byte of the data fieldof the previous segment exceeds the specific n bytes during the SDUsegmentation and transmission.

When a base station configures a terminal not to use an RLC serialnumber in order to reduce an overhead, the first operation may includean operation of transferring the RLC SDU to the lower layer withoutattaching the RLC header thereto (1-bit indicator may be included at thehead in order to indicate whether the segmentation operation has beenperformed) and an operation of transferring the RLC SDU to the lowerlayer through attaching of the 1-byte RLC header such as 1 i-31-1thereto (during configuring of the RLC header, the SI field is set to00, and the RLC header to which the SO field is not added isconfigured). If the base station does not configure the above-describedindication (nonuse of the serial number), the first operation mayinclude operations of setting the SI field to 00 when configuring theRLC header and configuring the RLC header to which the SO field is notadded.

The second operation may include operations of setting the SI field to01 when configuring the RLC header and configuring the RLC header towhich the SO field is not added.

The third operation may include setting the SI field to 11 whenconfiguring the RLC header, setting the ST field to 0 to indicate theuse of the short SO field, and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

The fourth operation may include setting the SI field to 10 whenconfiguring the RLC header, setting the ST field to 1 to indicate theuse of the long SO field, and configuring the RLC header so that anoffset can be indicated through addition of the SO field.

The receiving end may receive the RLC SDU, and identify the SI fieldfrom the RLC header to determine whether the received RLC SDU is the RLCSDU that has not been segmented (complete RLC SDU) or the RLC SDU thathas been segmented (segment). If the RLC SDU has not been segmented, thereceiving end may discard the RLC header and may send the RLC SDU to anupper layer. If the RLC SDU has been segmented, the receiving end mayidentify whether the RLC SDU is the first, middle, or last segment basedon the SI field, arrange the segments to match the RLC serial numbers inconsideration of the respective fields, such as identifying the lengthof the SO field, if any, through the ST field, and if a reassemblyfunction is triggered by a window or a timer, the receiving end may makea complete RLC SDU through reassembly of the segments to transfer thecomplete RLC SDU to the upper layer. If the reassembly of the segmentsis not possible, the RLC SDU is discarded.

In the RLC UM mode, the receiving end may operate based on the window orthe timer.

When the operation is based on the window, the receiving end may operatean

RLC reception window, and the window may be operated with a sizecorresponding to a half of the RLC serial number. When a lower edge ofthe window, a serial number through subtraction of the size of the RLCwindow from an upper edge may be configured, and the highest RLC serialnumber received from the receiving end RLC may be configured at theupper edge. Accordingly, if the received RLC serial number has a largervalue than the values of the RLC serial numbers in the window, thewindow moves accordingly. If the received RLC PDU serial number has asmaller value than the value of the received window lower edge, thereceiving end RLC layer may discard this, and may check whether aduplicate RLC PDU is received with respect to the RLC serial numberexisting in the window to discard the same.

Further, if an RLC PDU segment having an RLC serial number existing inthe window arrives, the receiving end RLC layer may store this, and ifthe lower edge of the window passes the RLC serial number correspondingto the RLC PDU segment, the receiving end RLC layer may generate andsend a complete RLC PDU through performing of a reassembling procedure.Conversely, if the complete RLC PDU is unable to be generated, thereceiving end RLC layer may discard the RLC PDU segments. The receivingend RLC layer may identify the SI field or 1-bit indicator, and maydirectly send the RLC PDU that has not been segmented to the upperlayer. Further, if the SI field or the 1-bit indicator indicates the RLCPDU that has been segmented, the receiving end RLC layer stores the RLCPDU segments, and if the reassembling procedure is triggered by thewindow as described above, it performs the reassembling procedure tosend the reassembled RLC PDU to the upper layer or to discard the same.

When the operation is based on the timer, the receiving end RLC layeroperates the timer in the RLC UM mode. The receiving end RLC layer mayoperate several timers or one timer.

When operating only one timer, the receiving end RLC layer identifiesthe SI field or 1-bit indicator, and directly sends the RLC PDU that hasnot been segmented to the upper layer. If the SI field or the 1-bitindicator indicates the RLC PDU that has been segmented, the receivingend RLC layer stores the RLC PDU segments, and operates the timer. Thatis, timer triggering is performed when the segmented RLC PDU segmentarrives.

Thereafter, if the RLC PDUs are received, the above-described process isrepeated, and if the RLC PDU segment has arrived again, the receivingend RLC layer identifies whether the timer is operated, and if the timeris not operated, the receiving end RLC layer restarts the timer. If thetimer expires, the receiving end RLC layer reassembles the RLC PDUsegments received up to now, and sends the reassembly-completed completeRLC PDUs to the upper layer while discarding the reassembly-failed RLCPDU segments.

When operating several timers, the receiving end RLC layer identifiesthe SI field or 1-bit indicator, and directly sends the RLC PDU that hasnot been segmented to the upper layer. If the SI field or the 1-bitindicator indicates the RLC PDU that has been segmented, the receivingend RLC layer stores the RLC PDU segments, and operates the timer withrespect to the RLC serial numbers of the RLC PDU segments. That is,timer triggering is performed when the segmented RLC PDU segmentcorresponding to a specific RLC serial number arrives.

Thereafter, if the RLC PDUs are received, the above-described process isrepeated, and if the RLC PDU segment has arrived again, the receivingend RLC layer identifies whether the timer corresponding to the RLCserial number of the received RLC PDU segment is operated, and if thetimer is not operated, the receiving end RLC layer restarts the timer.If the timer corresponding to the RLC serial number is not operated, thereceiving end RLC layer may operate a new timer with respect to thecorresponding RLC serial number. Accordingly, whenever the RLC PDUsegment arrives for each RLC serial number, the timer can be operatedfor each RLC serial number. If the timer for the specific RLC serialnumber expires, the receiving end RLC layer reassembles the RLC PDUsegments having the RLC serial numbers corresponding to the timerreceived up to now, and sends the reassembly-completed complete RLC PDUsto the upper layer while discarding the reassembly-failed RLC PDUsegments.

FIG. 1K is a diagram of a terminal, according to an embodiment.

The terminal includes a radio frequency (RF) processor 1 k-10, abaseband processor 1 k-20, a storage unit 1 k-30, and a controller 1k-40.

The RF processor 1 k-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. The RFprocessor 1 k-10 performs up-conversion of a baseband signal providedfrom the baseband processor 1 k-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 1 k-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a digital-to-analogconverter (DAC), and an analog-to-digital converter (ADC). Although onlyone antenna is illustrated, the terminal may be provided with aplurality of antennas. Further, the RF processor 1 k-10 may include aplurality of RF chains. Further, the RF processor 1 k-10 may performbeamforming. For the beamforming, the RF processor 1 k-10 may adjustphases and sizes of signals transmitted or received through theplurality of antennas or antenna elements. Further, the RF processor mayperform MIMO, and may receive several layers during performing of a MIMOoperation. The RF processor 1 k-10 may perform reception beam sweepingthrough proper configuration of the plurality of antennas or antennaelements under the control of the controller, or may control thedirection and the beam width of the reception beam so that the receptionbeam is synchronized with the transmission beam.

The baseband processor 1 k-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the system. During data transmission, the baseband processor 1 k-20generates complex symbols by encoding and modulating a transmitted bitstring. During data reception, the baseband processor 1 k-20 restores areceived bit string by demodulating and decoding the baseband signalprovided from the RF processor 1 k-10. For example, when following anOFDM method, during data transmission, the baseband processor 1 k-20generates complex symbols by encoding and modulating a transmitted bitstring, performs mapping of the complex symbols on subcarriers, and thenconfigures OFDM symbols through the inverse fast Fourier transform(IFFT) operation and cyclic prefix (CP) insertion. During datareception, the baseband processor 1 k-20 divides the baseband signalprovided from the RF processor 1 k-10 in the unit of OFDM symbols,restores the signals mapped on the subcarriers through the fast Fourier(FFT) operation, and then restores the received bit string throughdemodulation and decoding.

The baseband processor 1 k-20 and the RF processor 1 k-10 transmit andreceive the signals as described above. The baseband processor 1 k-20and the RF processor 1 k-10 may be called a transmitter, a receiver, atransceiver, or a communication unit. In order to support differentradio connection technologies, the baseband processor 1 k-20 and/or theRF processor 1 k-10 may include a plurality of communication modules. Inorder to process signals of different frequency bands, the basebandprocessor 1 k-20 and/or the RF processor 1 k-10 may include differentcommunication modules. For example, the different radio connectiontechnologies may include an LTE network and an NR network. Further, thedifferent frequency bands may include super high frequency (SHF) (e.g.,2.5 GHz or 5 GHz) band and millimeter wave (mmWave) (e.g., 60 GHz) band.

The storage unit 1 k-30 stores a basic program for an operation of theterminal, application programs, and data of setup information. Thestorage unit 1 k-30 provides stored data in accordance with a requestfrom the controller 1 k-40.

The controller 1 k-40 controls the operation of the terminal. Forexample, the controller 1 k-40 transmits and receives signals throughthe baseband processor 1 k-20 and the RF processor 1 k-10. Thecontroller 1 k-40 records or reads data in or from the storage unit 1k-30. The controller 1 k-40 may include at least one processor. Forexample, the controller 1 k-40 may include a communication processor forcontrolling communication and an AP for controlling an upper layer, suchas an application program. The controller 1 k-40 may include amulti-connection processor 1 k-42 for performing a process to operate ina multi-connection mode.

FIG. 1L is a diagram of a base station in a wireless communicationsystem, according to an embodiment.

The base station includes an RF processor 1 l-10, a baseband processor 1l-20, a backhaul communication unit 1 l-30, a storage unit 1 l-40, and acontroller 1 l-50.

The RF processor 1 l-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. The RFprocessor 1 l-10 performs up-conversion of a baseband signal providedfrom the baseband processor 1 l-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 1 l-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the base station may beprovided with a plurality of antennas. Further, the RF processor 1 l-10may include a plurality of RF chains. The RF processor 1 l-10 mayperform beamforming. For the beamforming, the RF processor 1 l-10 mayadjust phases and sizes of signals transmitted or received through theplurality of antennas or antenna elements. Further, the RF processor mayperform down MIMO operation through transmission of one or more layers.

The baseband processor 1 l-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the first radio connection technology. During data transmission, thebaseband processor 1 l-20 generates complex symbols by encoding andmodulating a transmitted bit string. During data reception, the basebandprocessor 1 l-20 restores a received bit string by demodulating anddecoding the baseband signal provided from the RF processor 1 l-10. Forexample, when following an OFDM method, during data transmission, thebaseband processor 1 l-20 generates complex symbols by encoding andmodulating a transmitted bit string, performs mapping of the complexsymbols on subcarriers, and then configures OFDM symbols through theIFFT operation and CP insertion. During data reception, the basebandprocessor 1 l-20 divides the baseband signal provided from the RFprocessor 1 l-10 in the unit of OFDM symbols, restores the signalsmapped on the subcarriers through the FFT operation, and then restoresthe received bit string through demodulation and decoding. The basebandprocessor 1 l-20 and the RF processor 1 l-10 transmit and receive thesignals as described above. Accordingly, the baseband processor 1 l-20and the RF processor 1 l-10 may be called a transmitter, a receiver, atransceiver, or a wireless communication unit.

The communication unit 1 l-30 provides an interface for communicatingwith other nodes in the network.

The storage unit 1 l-40 stores a basic program for an operation of themain base station, application programs, and data of setup information.In particular, the storage unit 1 l-40 may store information on a bearerallocated to the connected terminal and the measurement result reportedfrom the connected terminal. The storage unit 1 l-40 may storeinformation that becomes a basis of determination whether to provide orsuspend a multi-connection to the terminal. The storage unit 1 l-40provides stored data in accordance with a request from the controller 1l-50.

The controller 1 l-50 controls the base station. The controller 1 l-50transmits and receives signals through the baseband processor 1 l-20 andthe RF processor 1 l-10 or through the backhaul communication unit 1l-30. The controller 1 l-50 records or reads data in or from the storageunit 1 l-40. The controller 1 l-50 may include at least one processor.The controller 1 l-50 may include a multi-connection processor 1 l-52for performing a process to operate in a multi-connection mode.

FIG. 2A is a diagram of an LTE system, according to an embodiment.

Referring to FIG. 2A, a RAN of an LTE system is composed of eNBs, nodeBs, or base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20, an MME 2 a-25,and as S-GW 2 a-30. UE or terminal 2 a-35 accesses to an externalnetwork through the eNBs 2 a-05 to 2 a-20 and the S-GW 2 a-30.

In FIG. 2A, the eNBs 2 a-05 to 2 a-20 correspond to existing node Bs ofa UMTS system. The eNBs are connected to the UE 2 a-35 on a radiochannel, and play a more complicated role than that of the existing nodeB. In the LTE system, since all user traffics including a real-timeservice, such as a VoIP through an internet protocol, are serviced onshared channels, devices performing scheduling through summarization ofstate information, such as a buffer state, an available transmissionpower state, and a channel state of each UE, are necessary, and the eNBs2 a-05 to 2 a-20 control this. In general, one eNB controls a pluralityof cells. In order to implement a transmission speed of 100 Mbps, theLTE system uses OFDM in a bandwidth of 20 MHz as a radio accesstechnology (RAT). Further, the LTE system adopts an AMC scheme thatdetermines a modulation scheme and a channel coding rate to match thechannel state of the terminal. The S-GW 2 a-30 provides a data bearer,and generates or removes the data bearer under the control of the MME 2a-25. The MME controls not only mobility management of the terminal butalso various kinds of control functions, and is connected to theplurality of eNBs.

FIG. 2B is a diagram of a radio protocol structure in an LTE system,according to an embodiment.

Referring to FIG. 2B, in UE or an eNB, a radio protocol of an LTE systemis composed of a PDCP 2 b-05 or 2 b-40, an RLC 2 b-10 or 2 b-35, and aMAC 2 b-15 or 2 b-30. The PDCP 2 b-05 or 2 b-40 controls IP headercompression/decompression operations. The main functions of the PDCP aresummarized as follows:

Header compression and decompression: ROHC only;

Transfer of user data;

In-sequence delivery of upper layer PDUs at a PDCP reestablishmentprocedure for an RLC AM;

For split bearers in DC (only support for an RLC AM): PDCP PDU routingfor transmission and PDCP PDU reordering for reception;

Duplicate detection of lower layer SDUs at a PDCP reestablishmentprocedure for an RLC AM;

Retransmission of PDCP SDUs at handover and, for split bearers in DC, ofPDCP PDUs at a PDCP data-recovery procedure, for an RLC AM;

Ciphering and deciphering;

Timer-based SDU discard in an uplink; and

The radio link control (RLC) 2 b-10 or 2 b-35 reconfigures a PDCP PDUwith a proper size and performs an ARQ operation and the like.

The main functions of the RLC are summarized as follows:

Transfer of upper layer PDUs;

Error correction through an ARQ (only for AM data transfer);

Concatenation, segmentation, and reassembly of RLC SDUs (only for UM andAM data transfer);

Re-segmentation of RLC data PDUs (only for AM data transfer);

Reordering of RLC data PDUs (only for UM and AM data transfer);

Duplicate detection (only for UM and AM data transfer);

Protocol error detection (only for AM data transfer);

RLC SDU discard (only for UM and AM transfer); and

RLC reestablishment.

The MAC 2 b-15 or 2 b-30 is connected to several RLC layer devicesconfigured in one terminal, and performs multiplexing/demultiplexing ofRLC PDUs into/from MAC PDU. The main functions of the MAC are summarizedas follows:

Mapping between logical channels and transport channels;

Multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels;

Scheduling information reporting;

HARQ function (error correction through HARQ);

Priority handling between logical channels of one UE;

Priority handling between UEs by means of dynamic scheduling;

MBMS service identification;

Transport format selection; and

Padding.

The physical layer 2 b-20 or 2 b-25 performs channel coding andmodulation of upper layer data to configure and transmit OFDM symbols ona radio channel, or performs demodulation and channel decoding of theOFDM symbols received on the radio channel to transfer the demodulatedand channel-decoded symbols to an upper layer.

FIGS. 2CA and 2CB are diagrams of multi-connection and carrieraggregation operations of an existing LTE system, according to anembodiment.

Referring to FIGS. 2CA and 2CB, when eNB 1 2 c-05 transmits/receives acarrier having a center frequency of f1, and eNB 2 2 c-15transmits/receives a carrier having a center frequency of f2, one UE 1 2c-01 may perform transmission/reception with two or more eNBs throughcombination of a carrier having a forward center frequency of f1 and acarrier having a forward center frequency of f2. In an LTE system, theabove-described operation is supported, and referred to as dualconnectivity (DC).

Further, one eNB 3 can transmit and receive multi-carriers over severalfrequency bands. For example, if a carrier 2 c-30 having a forwardcenter frequency of f3 and a carrier 2 c-35 having a forward centerfrequency of f4 are transmitted from eNB 3 2 c-25, one UE 2transmits/receives data using one of the two carriers. However, the UE 2having a carrier aggregation capability can simultaneouslytransmit/receive data through several carriers. The eNB 3 2 c-35 mayallocate more carriers to the UE 2 2 c-40 having the carrier aggregationcapability according to circumstances to heighten the transmission speedof the UE 2 2 c-40. Aggregation of forward carriers and backwardcarriers transmitted and received by one eNB is referred to as intra-eNBcarrier aggregation (CA). Traditionally, if it is assumed that oneforward carrier transmitted by one eNB and one backward carrier receivedby the eNB constitute one cell, it may be understood that the carrieraggregation is for the UE to transmit/receive data simultaneouslythrough several cells. Through this, the maximum transmission speed isincreased in proportion to the number of carriers being aggregated.

Hereinafter, reception of data by the UE through a certain forwardcarrier or transmission of data by the UE through a certain uplinkcarrier is the same as transmission/reception of data using a controlchannel and a data channel provided from a cell corresponding to thecenter frequency and the frequency band featuring the carrier. A set ofserving cells being controlled by the same eNB is defined as a cellgroup (CG). The cell group is divided into a master cell group (MCG) anda secondary cell group (SCG). The MCG is a set of serving cells beingcontrolled by the eNB (master eNB (MeNB)) controlling a primary cell(PCell), and the SCG is a set of serving cells being controlled by theeNB that is not the eNB controlling the PCell. That is, being controlledby the eNB (secondary eNB (SeNB)) controlling only secondary cells(SCells). The eNB notifies the UE whether a specific serving cellbelongs to the MCG or the SCG in the process of configuring thecorresponding serving cell.

The PCell and SCell represent the kind of serving cell configured in theUE. There are some differences between the PCell and SCell, for example,the PCell always maintains an active state, but the SCell repeats anactive state and an inactive state in accordance with the indication ofthe eNB. The terminal mobility is controlled around the PCell, and itmay be understood that the SCell is an additional serving cell for datatransmission/reception. The PCell and the SCell are defined in the LTEstandards 36.331 or 36.321, and these terms have the same meanings asthose typically used in an LTE mobile communication system. The termscarrier, component carrier, and serving cell are used hereininterchangeably.

Referring again to FIGS. 2CA and 2CB, if eNB 1 2 c-05 is MeNB and eNB 22 c-15 is SeNB, a serving cell 2 c-10 having a center frequency of f1 isa serving cell belonging to the MCG, and a serving cell 2 c-20 having acenter frequency of f2 is a serving cell belonging to the SCG. Further,it may be difficult to transmit HARQ feedback of SCG SCells and channelstate information (CSI) through a physical uplink control channel(PUCCH) of a PCell. The HARQ feedback should be transferred within anHARQ round trip time (RTT) (normally, 8 ms), and the transmission delaybetween the MeNB and the SeNB may be longer than the HARQ RTT. Thus, aPUCCH transmission resource is configured in one of the SCells belongingto the SCG, that is, in a primary SCell (PSCell), the HARQ feedback ofthe SCG SCells, and the CSI are transmitted through the PUCCH.

Further, in a CA in a normal eNB 3 2 c-25, UE 2 2 c-40 transmits throughthe PUCCH of the PCell not only the HARQ feedback of the PCell and theCSI, but also the HARQ feedback of the SCell and the CSI. This is toapply the CA operation evenly with respect to the UE, in whichsimultaneous uplink transmission is difficult or impossible. In LTERel-13 (Release-13) enhanced CA (eCA), an additional SCell having aPUCCH is defined, and up to 32 carriers can be concatenated.

FIG. 2D is a diagram of a next-generation mobile communication system,according to an embodiment.

Referring to FIG. 2D, a RAN of a next-generation mobile communicationsystem is composed of aNR NB 2 d-10 and a new radio core network (NR CN)2 d-05. New radio user equipment (NR UE or terminal) 2 d-15 accesses toan external network through the NR NB 2 d-10 and the NR CN 2 d-05.

In FIG. 2D, the NR NB 2 d-10 corresponds to an eNB of the existing LTEsystem. The NR NB is connected to the NR UE 2 d-15 on a radio channel,and thus it can provide a superior service than the service of theexisting node B. Since all user traffics are serviced on shared channelsin the next-generation mobile communication system, a device thatperforms scheduling through consolidation of status information, such asa buffer state of UEs, an available transmission power state, and achannel state, is required, and the NR NB 2 d-10 controls thisoperation.

One NR NB generally controls a plurality of cells. In order to implementultrahigh-speed data transmission as compared with the existing LTE, theNR NB may have a bandwidth that is greater than or equal to the existingmaximum bandwidth, and a beamforming technology may be additionallygrafted in consideration of OFDM as a RAT. Further, an AMC schemedetermining a modulation scheme and a channel coding rate to match thechannel state of the UE is applied. The NR CN 2 d-05 performs functionsof mobility support, bearer setup, and QoS configuration. The NR CN is adevice that controls not only a mobility management function of the UEbut also various kinds of control functions, and is connected to aplurality of eNBs. Further, the next-generation mobile communicationsystem may interlock with the existing LTE system, and the NR CN isconnected to an MME 2 d-25 through a network interface. The MME isconnected to an eNB 2 d-30 that is the existing eNB.

FIG. 2E is a diagram of data transmission operation through packetduplication, according to an embodiment.

A method for transmitting duplicated data in different paths or ondifferent time resources when UE performs packet duplication to supportultra-reliable low latency communication (URLLC) in a next-generationmobile communication system is described herein. If the duplicated datais allocated to the same MAC PDU, duplicate transmission becomesimpossible. In case of the packet duplication, DC or CA may be used.That is, the UE should be in a state where the SgNB or SCell has beenconfigured so that the terminal can support the DC or CA. It is assumedthat the CA has been configured, and various methods for supportingpacket duplicate transmission will be described through variousexamples.

Referring again to FIG. 2E, the eNB or the UE receives a data packet forthe URLLC, that is, PDCP SDU1, from an upper layer (at step 2 e-05), andtransfers this to a PDCP layer. At step 2 e-10, the PDCP determineswhether to duplicate the corresponding data packet, and if the duplicateis necessary, it generates the original PDCP PDU1 and duplicated PDCPPDU2 (at steps 2 e-15 and 2 e-20) to transfer them to RLC layers atsteps 2 e-25 and 2 e-30. RLC1 and RLC2 of each serving cell transfer thereceived data packet to a MAC layer of the MgNB or the UE. At step 2e-35, the MAC layer generates a MAC PDU after mapping the receivedpacket data to a proper logical channel group (LCG), and transfers theMAC PDU to physical layers at steps 2 e-40 and 2 e-45 of thecorresponding serving cell. Thereafter, the physical layer transmits theMAC PDU transferred on the corresponding carrier aggregation or timeresources.

A receiving process is in reverse to the transmitting process. That is,the physical layer receives the data packet (MAC PDU) through thecorresponding serving cells (at steps 2 e-50 and 2 e-55), and transfersthe received data packet to the MAC layer of the UE or the MgNB (at step2 e-60). Thereafter, the PDCP PDU1 at step 2 e-75 and the PDCP PDU2 atstep 2 e-80 through the RLC1 and RLC2 at steps 2 e-65 and 2 e-70 aregathered to the PDCP of the UE or the MgNB, and the PDCP at step 2 e-85identifies SNs of the received original packet and the duplicatedpacket, and if the same packets arrive, it discards one of them totransfer the other to the upper layer (at step 2 e-90).

FIG. 2F is a diagram of a first data packet duplicate transmissionoperation, according to an embodiment.

A PDCP layer at step 2 f-05 determines whether to duplicate acorresponding data packet (PDCP SDU) at steps 2 f-10 (2 f-15), and ifthe duplicate is necessary, it configures the original (PDCP PDU1) atstep 2 f-20 and a duplicate (PDCP PDU2) at step 2 f-25 with respect tothe corresponding data packet to transfer them to a lower layer. Asdescribed above, since a resource should not be allocated so that alldata are transmitted from one MAC PDU, the duplicated data packet shouldbe transmitted from the MAC PDU on different carriers or on differenttime resources.

The first data packet duplicate transmission operation is a method tomap the PDCP data to be duplicated to different LCGs from the originalPDCP data packet (one PDCP entity is mapped to two LCGs). That is, ifthe PDCP data duplication is applied, a set of cells to which initiallytransmitted data and duplicated data can be transmitted is newly definedand applied. As the set of the cells, LCG cell group 1 at step 2 f-30and LCG cell group 2 at step 2 f-35 are used. That is, if initialtransmission of a certain PDCP PDU is performed through the LCG cellgroup 1, the transmission of the duplicated PDCP PDU is performedthrough the LCG cell group 2. The LCG cell groups may be respectivelymapped to specific LCG x at step 2 f-40 and LDB y at step 2 f-45. Thegreatest feature of the first data packet duplicate transmissionoperation is to map the original to LCG x and to map the duplicate toLCG y even in case of one piece of PDCP data.

FIG. 2G is a diagram of a second data packet duplicate transmissionoperation proposed, according to an embodiment.

A PDCP layer at step 2 g-05 determines whether to duplicate acorresponding data packet (PDCP SDU) at step 2 g-10 (and/or at step 2g-15), and if the duplicate is necessary, it configures the original(PDCP PDU1) at step 2 g-20 and a duplicate (PDCP PDU2) at step 2 g-25with respect to the corresponding data packet to transfer them to alower layer. As described above, since a resource should not beallocated so that all data are transmitted from one MAC PDU, theduplicated data packet should be transmitted from the MAC PDU ondifferent carriers or on different time resources.

If a PDCP entity to which duplication is to be applied is mapped to oneLCG, that is, if the original PDCP data and the duplicated PDCP data aremapped to the same LCG, the resources should be allocated differently soas to be transmitted from different MAC PDUs. If a duplicated PDCP PDU(PDCP PDU of which duplicate transmission has not yet started, butduplicate transmission should be performed) exists when regular bufferstatus reports (BSRs) at steps 2 g-35 and 2 g-40 for the original PDCPdata are triggered, a supplemental BSR that is a new BSR is triggeredtogether (at step 2 g-30). The supplemental BSR is to report the amountof PDCP data only to be duplicated and transmitted, and is composed ofan LCG ID and a buffer size (BS) (at step 2 g-45). The supplemental BSRmay have formats of the existing short regular BSR and long regular BSR(at steps 2 g-60 and 2 g-65). Further, if the supplemental BSR isincluded in the MAC PDU, the corresponding indicator is included in aMAC subheader. For example, the following situations shown in Table 4below may be considered.

TABLE 4 Situation Operation Situation Original and duplicate dataSupplemental BSR having 1 packets are mapped to LCG 1. the same formatand size as Original packet: SRB 1 those of short regular BSR Duplicatepacket: SRB 1 is generated. (same packet duplication) Situation Originaland duplicate data Supplemental BSR 2 packets are mapped to LCG 1.including SRB 2 size Original packet: SRB 1, SRB 2 information isgenerated. Duplicate packet: SRB 2 (partial packet duplication)Situation Original and duplicate data Supplemental BSR having 3 packetsare mapped to LCG 1. the same format and size as Original packet: SRB 1,SRB 2, those of long regular BSR SRB 3 is generated. Duplicate packet:SRB 1, SRB 2, SRB 3 (whole packet dupli- cation)

FIG. 2H is a diagram of an operation to which a first data packetduplicate transmission operation is applied, according to an embodiment.

UE 2 h-01 in an idle mode (RRC_IDLE) searches for a suitable cell andcamps on a corresponding serving cell 2 h-02 (at step 2 h-05), andreceives system information from the serving cell 2 h-02 (at step 2h-10). In the idle mode, the UE 2 h-01 is not connected to a network forpower saving, and thus is unable to transmit data. For datatransmission, the UE 2 h-01 is required to be shifted to a connectedmode (RRC_CONNECTED) (at step 2 h-15). Further, the term camps on isdefined as the UE staying in the corresponding cell to receive a pagingmessage in order to determine whether data comes on a downlink.

PCell 2 h-02 of the serving eNB 2 h-04 adds SCell 2 h-03 (at step 2h-20), and transfers to the UE 2 h-01 an RRCConnectionReconfigurationmessage containing bearer configuration information on the SCell 2 h-03and packet duplicate activation information (at step 2 h-25). Althoughis omitted in the drawing, the method for the serving eNB 2 h-04 to addthe SCell 2 h-03 becomes possible depending on whether URLLC data isgenerated (capability or URLLC request) from the UE 2 h-01. Further, theUE 2 h-01 may report a measurement value of a downlink signal strengthof a neighbor cell to the PCell 2 h-02 of the serving eNB 2 h-04. TheSCell 2 h-03 is a bearer configured for the URLLC transmission, and isgenerated by configuring an additional LCG cell group and acorresponding serving cell through the RRCConnectionReconfigurationmessage. The UE 2 h-01 transmits an RRCConnectionReconfigurationCompletemessage containing an identification message with respect to the SCell 2h-03 configuration for the URLLC (at step 2 h-30), and reconfigures theMAC through addition of the SCell 2 h-03 for the URLLC in accordancewith the configured value (at step 2 h-35).

If data is generated in the URLLC mode, the first data packet duplicatetransmission operation as described above with reference to FIG. 2F isperformed. That is, the data to be duplicated is mapped to differentLCGs (the initially transmitted PDCP PDU is mapped to LCG cell group 1,and the duplicate PDCP PDU is mapped to LCG cell group 2). At theabove-described operation, the MAC makes the original data packet andthe duplicated data packet mapped to different LCGs, and thereafter,triggers the regular BSR in accordance with the respective LCGs (at step2 h-40). At step 2 h-45, the UE 2 h-01 transfers the regular BSR mappedto the different LCGs to the serving eNB 2 h-04. For example, the BSRsignals may be transmitted through the PCell 2 h-02, or may berespectively transmitted through the PCell 2 h-02 and the SCell 2 h-03.

The serving eNB 2 h-04 allocates resources based on the regular BSRreceived from the UE 2 h-01, and the UE 2 h-01 transmits or receivesdata through the allocated resources (at step 2 h-55). The serving eNB 2h-04 can know the original data and the duplicated data through an LCGID included in the regular BSR, and through this information, it canallocate independent resources to the UE 2 h-01 through the respectivecarrier aggregations with respect to the original and the duplicatedata.

FIG. 2I is a diagram of an overall operation to which a second datapacket duplicate transmission operation is applied, according to anembodiment.

UE 2 i-01 in an idle mode (RRC_IDLE) searches for a suitable cell andcamps on a corresponding serving cell 2 i-02 (at step 2 i-05), andreceives system information from the serving cell 2 i-02 (at step 2i-10). In the idle mode, the UE 2 i-01 is not connected to a network forpower saving, and thus is unable to transmit data. For datatransmission, the UE 2 i-01 is required to be shifted to a connectedmode (RRC_CONNECTED) (2 i-15).

PCell 2 i-02 of the serving eNB 2 i-04 adds SCell 2 i-03 (at step 2i-20), and transfers to the UE 2 i-01 an RRCConnectionReconfigurationmessage containing bearer configuration information on the SCell 2 i-03and packet duplicate activation information (at step 2 i-25). It isnoted that the method for the serving eNB 2 i-04 to add the SCell 2 i-03becomes possible depending on whether URLLC data is generated(capability or URLLC request) from the UE 2 i-01. Further, the UE 2 i-01may report a measurement value of a downlink signal strength of aneighbor cell to the PCell 2 i-02 of the serving eNB 2 i-04. The SCell 2i-03 is a bearer configured for the URLLC transmission, and is generatedby configuring an additional LCG cell group and a corresponding servingcell through the RRCConnectionReconfiguration message. The UE transmitsan RRCConnectionReconfigurationComplete message containing anidentification message with respect to the SCell 2 i-03 configurationfor the URLLC and packet duplicate activation information (at step 2i-30), and reconfigures the MAC through addition of the SCell 2 i-03 forthe URLLC in accordance with the configured value (at step 2 i-35).

If data is generated in the URLLC mode, the regular BSR is triggered,and if a duplicated PDCP PDU (PDCP PDU of which duplicate transmissionhas not yet started, but duplicate transmission should be performed)exists when the regular BSR for the original PDCP data is triggered, asupplemental BSR that is a new BSR is triggered together. The seconddata packet duplicate transmission operation as described above withreference to FIG. 2G is performed. At the above-described operation, theMAC triggers together the supplemental BSR including the amount of PDCPdata to be duplicated and transmitted (at step 2 i-40).

At step 2 i-45, the UE 2 i-01 transfers the generated regular BSR andsupplemental BSR to the corresponding serving eNB 2 i-04. For example,the BSR signals may be transmitted through the PCell 2 i-02, or may berespectively transmitted through the PCell 2 i-02 and the SCell 2 i-03.The serving eNB 2 i-04 allocates resources based on the regular BSR andthe supplemental BSR received from the UE 2 i-01, and the UE 2 i-01transmits or receives data through the allocated resources (at step 2i-55). The serving eNB 2 i-04 can know what data is the original data orthe duplicated data and what sizes are necessary through reception ofthe regular BSR and the supplemental BSR, and through this information,it can allocate independent resources to the UE 2 i-01 through therespective carrier aggregations with respect to the original and theduplicate data.

FIG. 2J is a diagram of a first data packet duplicate transmissionoperation of a terminal, according to an embodiment.

A UE configures a connection with an eNB for data transmission/reception(at step 2 j-05), and receives an RRC message containing SCellconfiguration for URLLC from the eNB. The SCell bearer is a bearerconfigured for the URLLC transmission, and an additional LCG cell groupand a corresponding serving cell may be configured by the RRC message(at step 2 j-10). Further, the UE receives indication information onpacket duplicate function activation from the eNB. The UE havingreceived the configuration from the eNB reconfigures the MAC inaccordance with the configuration value (at step 2 j-15), and performsURLLC data generation and a first data packet duplicate transmissionoperation. That is, the data to be duplicated is mapped to differentLCGs (the initially transmitted PDCP PDU is mapped to LCG cell group 1,and the duplicate PDCP PDU is mapped to LCG cell group 2). At theabove-described operation, the MAC makes the original data packet andthe duplicated data packet mapped to different LCGs, and thereafter,triggers the regular BSR in accordance with the respective LCGs (at step2 j-20). Thereafter, the UE transfers the generated regular BSR to theeNB (at step 2 j-25), and performs data transmission/reception throughcarrier aggregation with the resource allocated from the eNB (at step 2j-30). At the above-described operation, the UE may transmit theoriginal data packet and the duplicate data packet through differentcarrier components (e.g., PCell and SCell). The serving eNB knows whatdata is the original data or the duplicated data through an LCG IDincluded in the regular BSR, and through the LCG ID, it can allocateindependent resources to the UE through the respective carrieraggregations with respect to the original and the duplicate data.

FIG. 2K is a diagram of a second data packet duplicate transmissionoperation of a terminal, according to an embodiment.

A UE configures a connection with an eNB for data transmission/reception(at step 2 k-05), and receives an RRC message containing SCellconfiguration for URLLC from the eNB. The SCell bearer is a bearerconfigured for the URLLC transmission, and an additional LCG cell groupand a corresponding serving cell may be configured by the RRC message(at step 2 k-10). Further, the UE receives indication information onpacket duplicate function activation from the eNB. The UE havingreceived the configuration from the eNB reconfigures the MAC inaccordance with the configuration value (at step 2 k-15), generatesURLLC data, and triggers regular BSR (at step 2 k-20). That is, if datais generated in the URLLC mode, the regular BSR is triggered, and it isidentified whether a duplicated PDCP PDU (PDCP PDU of which duplicatetransmission has not yet started, but duplicate transmission should beperformed) exists when the regular BSR for the original PDCP data istriggered (at step 2 k-25).

If the duplicated PDCP PDU exists when the regular BSR for the originalPDCP data is triggered, a supplemental BSR for the BSR of the duplicateddata packet is generated and triggered together (at step 2 k-30).Thereafter, the UE transmits the regular BSR and the supplemental BSR tothe serving eNB together (at step 2 k-35), and is allocated with thecorresponding resource. The serving eNB knows what data is the originaldata or the duplicated data and what sizes are necessary throughreception of the regular BSR and the supplemental BSR, and through thisinformation, it can allocate independent resources to the UE through therespective carrier aggregations with respect to the original and theduplicate data. The terminal transmits the original data packet and theduplicate data packet through different carrier components (e.g., PCelland SCell) through the allocated resources.

If the duplicated PDCP PDU does not exist when the regular BSR for theoriginal PDCP data is triggered, the packet duplication is not used, andin this case, the regular BSR for the original data packet istransferred to the eNB, and the corresponding resource is allocated (atstep 2 k-45). The terminal transmits the original data packet throughthe PCell through the allocated resource (at step 2 k-50).

FIG. 2L is a diagram of a terminal, according to an embodiment.

The terminal includes an RF processor 2 l-10, a baseband processor 2l-20, a storage unit 2 l-30, and a controller 2 l-40.

The RF processor 2 l-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. The RFprocessor 2 l-10 performs up-conversion of a baseband signal providedfrom the baseband processor 2 l-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 2 l-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the terminal may be providedwith a plurality of antennas. The RF processor 2 l-10 may include aplurality of RF chains. Further, the RF processor 2 l-10 may performbeamforming. For the beamforming, the RF processor 2 l-10 may adjustphases and sizes of signals transmitted or received through theplurality of antennas or antenna elements. Further, the RF processor mayperform MIMO, and may receive several layers during performing of a MIMOoperation.

The baseband processor 2 l-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the system. During data transmission, the baseband processor 2 l-20generates complex symbols by encoding and modulating a transmitted bitstring. During data reception, the baseband processor 2 l-20 restores areceived bit string by demodulating and decoding the baseband signalprovided from the RF processor 2 l-10. For example, when following anOFDM method, during data transmission, the baseband processor 2 l-20generates complex symbols by encoding and modulating a transmitted bitstring, performs mapping of the complex symbols on subcarriers, and thenconfigures OFDM symbols through the IFFT operation and CP insertion.During data reception, the baseband processor 2 l-20 divides thebaseband signal provided from the RF processor 2 l-10 in the unit ofOFDM symbols, restores the signals mapped on the subcarriers through theFFT operation, and then restores the received bit string throughdemodulation and decoding.

The baseband processor 2 l-20 and the RF processor 2 l-10 transmit andreceive the signals as described above. The baseband processor 2 l-20and the RF processor 2 l-10 may be called a transmitter, a receiver, atransceiver, or a communication unit. In order to support differentradio connection technologies, at least one of the baseband processor 2l-20 and the RF processor 2 l-10 may include a plurality ofcommunication modules. In order to process signals of differentfrequency bands, at least one of the baseband processor 2 l-20 and theRF processor 2 l-10 may include different communication modules. Forexample, the different radio connection technologies may include awireless LAN (e.g., IEEE 802.11) and a cellular network (e.g., LTE).Further, the different frequency bands may include SHF (e.g., 2.NRHz orNRHz) band and millimeter wave (mmWave) (e.g., 60 GHz) band.

The storage unit 2 l-30 stores a basic program for an operation of theterminal, application programs, and data of setup information. Inparticular, the storage unit 2 l-30 may store information related to aconnection node for performing wireless communication using a secondwireless connection technology. The storage unit 2 l-30 provides storeddata in accordance with a request from the controller 2 l-40. Thecontroller 2 l-40 controls the operation of the terminal. For example,the controller 2 l-40 transmits and receives signals through thebaseband processor 2 l-20 and the RF processor 2 l-10. The controller 2l-40 records or reads data in or from the storage unit 2 l-30. Thecontroller 2 l-40 may include at least one processor. The controller 2l-40 may include a communication processor performing a control forcommunication and an AP controlling an upper layer, such as anapplication program. The controller 2 l-40 may include amulti-connection processor 2 l-42 for performing a process to operate ina multi-connection mode.

FIG. 2M is a block diagram of a base station, according to anembodiment.

The base station includes an RF processor 2 m-10, a baseband processor 2m-20, a backhaul communication unit 2 m-30, a storage unit 2 m-40, and acontroller 2 m-50.

The RF processor 2 m-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. The RFprocessor 2 m-10 performs up-conversion of a baseband signal providedfrom the baseband processor 2 m-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 2 m-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the base station may beprovided with a plurality of antennas. The RF processor 2 m-10 mayinclude a plurality of RF chains. The RF processor 2 m-10 may performbeamforming. For the beamforming, the RF processor 2 m-10 may adjustphases and sizes of signals transmitted or received through theplurality of antennas or antenna elements. The RF processor may performdown MIMO operation through transmission of one or more layers.

The baseband processor 2 m-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the first radio connection technology. During data transmission, thebaseband processor 2 m-20 generates complex symbols by encoding andmodulating a transmitted bit string. During data reception, the basebandprocessor 2 m-20 restores a received bit string by demodulating anddecoding the baseband signal provided from the RF processor 2 m-10. Forexample, when following an OFDM method, during data transmission, thebaseband processor 2 m-20 generates complex symbols by encoding andmodulating a transmitted bit string, performs mapping of the complexsymbols on subcarriers, and then configures OFDM symbols through theIFFT operation and CP insertion. During data reception, the basebandprocessor 2 m-20 divides the baseband signal provided from the RFprocessor 2 m-10 in the unit of OFDM symbols, restores the signalsmapped on the subcarriers through the FFT operation, and then restoresthe received bit string through demodulation and decoding. The basebandprocessor 2 m-20 and the RF processor 2 m-10 transmit and receive thesignals as described above. Accordingly, the baseband processor 2 m-20and the RF processor 2 m-10 may be called a transmitter, a receiver, atransceiver, or a wireless communication unit.

The backhaul communication unit 2 m-30 provides an interface forperforming communication with other nodes in the network. The backhaulcommunication unit 2 m-30 converts a bit string transmitted from the eNBto another node, for example, an auxiliary base station or a corenetwork, into a physical signal, and converts a physical signal receivedfrom another node into a bit string.

The storage unit 2 m-40 stores a basic program for an operation of themain base station, application programs, and data of setup information.In particular, the storage unit 2 m-40 may store information on a bearerallocated to the connected terminal and the measurement result reportedfrom the connected terminal. The storage unit 2 m-40 may storeinformation that becomes a basis of determination whether to provide orsuspend a multi-connection to the terminal. The storage unit 2 m-40provides stored data in accordance with a request from the controller 2m-50.

The controller 2 m-50 controls the operation of the base station. Forexample, the controller 2 m-50 transmits and receives signals throughthe baseband processor 2 m-20 and the RF processor 2 m-10 or through thebackhaul communication unit 2 m-30. The controller 2 m-50 records orreads data in or from the storage unit 2 m-40. The controller 2 m-50 mayinclude at least one processor. According to an embodiment, thecontroller 2 m-50 may include a multi-connection processor 2 m-52 forperforming a process to operate in a multi-connection mode.

FIG. 3A is a diagram of an LTE system, according to an embodiment.

Referring to FIG. 3A, a RAT of an LTE system is composed of eNBs, nodeBs, or base stations) 3 a-05, 3 a-10, 3 a-15, and 3 a-20, a MME 3 a-25,and an S-GW 3 a-30. UE or terminal 3 a-35 accesses to an externalnetwork through the eNBs 3 a-05 to 3 a-20 and the S-GW 3 a-30.

In FIG. 3A, the eNBs 3 a-05 to 3 a-20 correspond to existing node Bs ofa UMTS system. The eNBs are connected to the UE 3 a-35 on a radiochannel, and play a more complicated role than that of the existing nodeB. In the LTE system, since all user traffics including a real-timeservice, such as a VoIP through an internet protocol, are serviced onshared channels, devices performing scheduling through summarization ofstate information, such as a buffer state, an available transmissionpower state, and a channel state of each UE, are necessary, and the eNBs3 a-05 to 3 a-20 take charge of this. In general, one eNB controls aplurality of cells. For example, in order to implement a transmissionspeed of 100 Mbps, the LTE system uses, for example, OFDM in a bandwidthof 20 MHz as a RAT. Further, the LTE system adopts an AMC scheme thatdetermines a modulation scheme and a channel coding rate to match thechannel state of the terminal. The S-GW 3 a-30 is a device that providesa data bearer, and generates or removes the data bearer under thecontrol of the MME 3 a-25. The MME is a device that controls not onlymobility management of the terminal but also various kinds of controlfunctions, and is connected to the plurality of eNBs.

FIG. 3B is a diagram of a radio protocol structure in an LTE system,according to an embodiment.

Referring to FIG. 3B, in a UE or an eNB, a radio protocol of an LTEsystem is composed of a PDCP 3 b-05 or 3 b-40, a RLC 3 b-10 or 3 b-35,and a MAC 3 b-15 or 3 b-30. The PDCP 3 b-05 or 3 b-40 controls IP headercompression/decompression operations. The main functions of the PDCP aresummarized as follows:

Header compression and decompression: ROHC only;

Transfer of user data;

In-sequence delivery of upper layer PDUs at a PDCP reestablishmentprocedure for an RLC AM;

For split bearers in DC (only support for an RLC AM): PDCP PDU routingfor transmission and PDCP PDU reordering for reception;

Duplicate detection of lower layer SDUs at a PDCP reestablishmentprocedure for an RLC AM;

Retransmission of PDCP SDUs at handover and, for split bearers in DC, ofPDCP PDUs at a PDCP data-recovery procedure, for an RLC AM;

Ciphering and deciphering; and

Timer-based SDU discard in an uplink.

The RLC 3 b-10 or 3 b-35 reconfigures a PDCP PDU with a proper size andperforms an ARQ operation and the like. The main functions of the RLCare summarized as follows:

Transfer of upper layer PDUs;

Error correction through an ARQ (only for AM data transfer);

Concatenation, segmentation, and reassembly of RLC SDUs (only for UM andAM data transfer);

Re-segmentation of RLC data PDUs (only for AM data transfer);

Reordering of RLC data PDUs (only for UM and AM data transfer);

Duplicate detection (only for UM and AM data transfer);

Protocol error detection (only for AM data transfer);

RLC SDU discard (only for UM and AM transfer); and

RLC reestablishment.

The MAC 3 b-15 or 3 b-30 is connected to several RLC layer devicesconfigured in one terminal, and performs multiplexing/demultiplexing ofRLC PDUs into/from MAC PDU. The main functions of the MAC are summarizedas follows:

Mapping between logical channels and transport channels;

Multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels;

Scheduling information reporting;

HARQ function (error correction through HARQ);

Priority handling between logical channels of one UE;

Priority handling between UEs by means of dynamic scheduling;

MBMS service identification;

Transport format selection; and

Padding.

The physical layer 3 b-20 or 3 b-25 performs channel coding andmodulation of upper layer data to configure and transmit OFDM symbols ona radio channel, or performs demodulation and channel decoding of theOFDM symbols received on the radio channel to transfer the demodulatedand channel-decoded symbols to an upper layer.

FIGS. 3CA and 3CB are diagrams of multi-connection and carrieraggregation operations of an existing LTE system, according to anembodiment.

Referring to FIGS. 3CA and 3CB, when eNB 1 3 c-05 transmits/receives acarrier having a center frequency of f1, and eNB 2 3 c-15transmits/receives a carrier having a center frequency of f2, one UE 3c-01 may perform transmission/reception with two or more eNBs throughcombination of a carrier having a forward center frequency of f1 and acarrier having a forward center frequency of f2. In an LTE system, theabove-described operation is supported, and is referred to as DC.

The one eNB can transmit and receive multi-carriers over severalfrequency bands. For example, if a carrier 3 c-30 having a forwardcenter frequency of f3 and a carrier 3 c-35 having a forward centerfrequency of f4 are transmitted from eNB 3 3 c-25, in the related art,one UE 2 3 c-40 transmits/receives data using one of the two carriers.However, the UE 2 having a CA capability can simultaneouslytransmit/receive data through several carriers. The eNB 3 3 c-35 mayallocate more carriers to the UE 2 3 c-40 having the CA capabilityaccording to circumstances to heighten the transmission speed of the UE2 3 c-40. As described above, aggregation of forward carriers andbackward carriers transmitted and received by one eNB is referred to asintra-eNB CA. Traditionally, if it is assumed that one forward carriertransmitted by one eNB and one backward carrier received by the eNBconstitute one cell, it may be understood that the CA is for the UE totransmit/receive data simultaneously through several cells. Throughthis, the maximum transmission speed is increased in proportion to thenumber of carriers being aggregated.

Reception of data by the UE through a certain forward carrier ortransmission of data by the UE through a certain uplink carrier has thesame meaning as transmission/reception of data using a control channeland a data channel provided from a cell corresponding to the centerfrequency and the frequency band featuring the carrier. A set of servingcells being controlled by the same eNB is defined as a CG. The cellgroup is divided into a MCG and a SCG. The MCG includes a set of servingcells being controlled by the eNB (master eNB (MeNB)) controlling aprimary cell (PCell), and the SCG includes a set of serving cells beingcontrolled by the eNB that is not the eNB controlling the PCell, inother words, being controlled by the eNB (secondary eNB (SeNB))controlling only secondary cells (SCells). The eNB notifies the UEwhether a specific serving cell belongs to the MCG or the SCG in theprocess of configuring the corresponding serving cell.

The PCell and SCell are terms representing the kind of serving cellconfigured in the UE. There are differences between the PCell and SCell,and for example, the PCell always maintains an active state, but theSCell repeats an active state and an inactive state in accordance withthe indication of the eNB. The terminal mobility is controlled aroundthe PCell, and it may be understood that the SCell is an additionalserving cell for data transmission/reception. The PCell and the SCellare defined in the LTE standards 36.331 or 36.321. The terms have thesame meanings as those used in an LTE mobile communication system. Theterms carrier, component carrier, and serving cell are usedinterchangeably.

Referring again to FIGS. 3CA and 3CB, if eNB 1 3 c-05 is MeNB and eNB 23 c-15 is SeNB, a serving cell 3 c-10 having a center frequency of f1 isa serving cell belonging to the MCG, and a serving cell 3 c-20 having acenter frequency of f2 is a serving cell belonging to the SCG. It may bedifficult to transmit HARQ feedback of SCG SCells and CSI through aphysical uplink control channel (PUCCH) of a PCell. The HARQ feedbackshould be transferred within an HARQ RTT (normally, 8 ms), and this isbecause the transmission delay between the MeNB and the SeNB may belonger than the HARQ RTT. Thus, a PUCCH transmission resource isconfigured in one of SCells belonging to the SCG, that is, in a primarySCell (PSCell), the HARQ feedback of the SCG SCells and the CSI aretransmitted through the PUCCH.

In a CA in a normal eNB 3 3 c-25, UE 2 3 c-40 transmits through thePUCCH of the PCell not only the HARQ feedback of the PCell and the CSIbut also the HARQ feedback of the SCell and the CSI. This is to applythe CA operation even with respect to the UE in which simultaneousuplink transmission is impossible. In LTE Rel-13 eCA, an additionalSCell having a PUCCH is defined, and up to 32 carriers can beconcatenated.

FIG. 3D is a diagram of a next-generation mobile communication system,according to an embodiment.

Referring to FIG. 3D, a RAN of a next-generation mobile communicationsystem is composed of an NR NB 3 d-10 and an NR CN 3 d-05. NR UE orterminal 3 d-15 accesses to an external network through the NR NB 3 d-10and the NR CN 3 d-05.

In FIG. 3D, the NR NB 3 d-10 corresponds to an eNB of the existing LTEsystem. The NR NB is connected to the NR UE 3 d-15 on a radio channel,and thus it can provide a superior service than the service of theexisting node B. Since all user traffics are serviced on shared channelsin the next-generation mobile communication system, a device thatperforms scheduling through consolidation of status information, such asa buffer state of UEs, an available transmission power state, and achannel state, is required, and the NR NB 3 d-10 controls thisoperation.

One NR NB generally controls a plurality of cells. In order to implementultrahigh-speed data transmission as compared with the existing LTE, theNR NB may have a bandwidth that is greater than or equal to the existingmaximum bandwidth, and a beamforming technology may be additionallygrafted in consideration of OFDM as a RAT. An AMC scheme determining amodulation scheme and a channel coding rate to match the channel stateof the UE is applied. The NR CN 3 d-05 performs functions of mobilitysupport, bearer setup, and QoS configuration. The NR CN is a device thatcontrols not only a mobility management function of the UE but alsovarious kinds of control functions, and is connected to a plurality ofeNBs. The next-generation mobile communication system may interlock withthe existing LTE system, and the NR CN is connected to an MME 3 d-25through a network interface. The MME is connected to an eNB 3 d-30 thatis the existing eNB.

A method for selectively performing path selection and packetduplication in accordance with the channel situations when UE performspacket duplication to support ultra-reliable low latency communication(URLLC) in a next-generation mobile communication system is provided.The packet duplication is used in the URLLC so that data receptionreliability can be heightened by duplicating and transmitting data or acontrol signal through two different paths to obtain high-reliabilitydata transmission and by acquiring transmission diversity through this.With respect to the packet duplication, DC or CA may be used. That is,the UE should be in a state where the SgNB or SCell has been configuredso that the terminal can support the DC or CA.

FIG. 3E is a diagram of a first operation in which an eNB performs pathselection and determination of duplicate transmission types, accordingto an embodiment.

UE 3 e-01 in an idle mode (RRC_IDLE) searches for a suitable cell andcamps on a corresponding eNB or MgNB 3 e-03 (at step 3 e-10), andreceives system information from the eNB 3 e-03 (at step 3 e-15). In theidle mode, the UE 3 e-01 is not connected to a network for power saving,and thus is unable to transmit data. For data transmission, the UE 3e-01 is required to be shifted to a connected mode (RRC_CONNECTED) (atstep 3 e-20). Thereafter, the UE 3 e-01 may report a measurement valueof a downlink signal strength of a neighbor cell or a cell belonging toa neighbor eNB to the eNB 3 e-03 (at step 3 e-25). The eNB 3 e-03 adds asecondary gNB (SgNB) 3 e-05 or a corresponding serving cell to thePSCell (at step 3 e-30), and transfers an RRCConnectionReconfigurationmessage containing bearer configuration information for the SgNB 3 e-05to the UE 3 e-01 (at step 3 e-35). The SgNB 3 e-05 bearer is a bearerconfigured for URLLC transmission, or additional LCG cell group andserving cell may be configured. The above-described configurationdiffers depending on whether the duplicate transmission is the duplicatetransmission using multi-connection or the duplicate transmission usingcarrier aggregation.

The UE 3 e-01 transmits an RRCConnectionReconfigurationComplete messageincluding an identification message to the SgNB 3 e-05 for URLLC orserving cell configuration (at step 3 e-40), and adds the SgNB 3 e-05for the URLLC or serving cell in accordance with the configuration value(at step 3 e-45). The eNB 3 e-03 determines what transmission type theUE performs data transmission/reception based on the channel measurementvalue received from the UE 3 e-01 (at step 3 e-50). The eNB 3 e-03 canarrange channel situations between the UE 3 e-01 and the eNB 3 e-03 orserving cells in Table 5 below. The eNB 3 e-03 can use the channelmeasurement value received from the UE 3 e-01 in accordance with Table 5below.

TABLE 5 Channel Situation Operation Situation Channel situation > Twopaths Transmission through a 1 exceeding threshold (two preferred pathpaths are good) (predesignated by eNB) or pre-transmittable pathSituation Channel situation > One path Transmission through a 2exceeding threshold (only one path having good situation path is good)Situation Channel situation > No path Duplicate transmission 3 exceedingthreshold (two applied paths are not good)

With respect to Situation 1 and Situation 2 in the above Table, the eNB3 e-03 determines and indicates the transmission path to the UE, andwith respect to Situation 3, the eNB 3 e-03 grasps the URLLC mode, andindicates to use both the two paths by applying the packet duplicatetransmission (at step 3 e-55). The UE 3 e-01 having received thistransmits an identification message through anRRCConnectionReconfigurationComplete message (at step 3 e-60), andperforms data transmission/reception in accordance with the receivedtransmission type (at step 3 e-65). That is, the UE 3 e-01 performs datatransmission/reception through one configured path of eNB 3 e-03 or SgNB3 e-05, or performs packet duplicate transmission using both the twopaths if the packet duplication is determined.

FIG. 3F is a diagram of a second operation in which UE performs pathselection and duplicate transmission type according, according to anembodiment.

UE 3 f-01 in an idle mode (RRC_IDLE) searches for a suitable cell andcamps on a corresponding eNB or MgNB 3 f-03 (at step 3 f-10), andreceives system information from the eNB 3 f-03 (at step 3 f-15). In theidle mode, the UE 3 f-01 is not connected to a network for power saving,and thus is unable to transmit data. For data transmission, the UE 3f-01 is required to be shifted to a connected mode (RRC_CONNECTED) (atstep 3 f-20). Thereafter, the UE 3 f-01 may report a measurement valueof a downlink signal strength of a neighbor cell or a cell belonging toa neighbor eNB to the eNB 3 f-03 (at step 3 f-25). The eNB 3 f-03 adds asecondary gNB (SgNB) 3 e-05 for URLLC or a corresponding serving cell tothe PSCell (at step 3 f-30), and transfers anRRCConnectionReconfiguration message containing bearer configurationinformation for the SgNB 3 e-05 to the UE 3 f-01 (at step 3 f-35). TheSgNB 3 e-05 bearer is a bearer configured for URLLC transmission, oradditional LCG cell group and serving cell may be configured. Theabove-described configuration differs depending on whether the duplicatetransmission is the duplicate transmission using multi-connection or theduplicate transmission using carrier aggregation. In the RRC message, areference channel situation required for the UE 3 f-01 to determine thetransmission method may be configured. The eNB 3 f-03 can arrangechannel situations between the UE 3 f-01 and the eNB 3 f-03 or servingcells in Table 6 below, and can transfer information indicating this tothe UE 3 f-01. That is, the RRC message includes a preferred path forSituation 1 and threshold information for determining the channelsituation, as shown in Table 6 below.

TABLE 6 Channel Situation Operation Situation Channel situation > Twopaths Transmission through a 1 exceeding threshold (two preferred pathpaths are good) (predesignated by eNB) or pre-transmittable pathSituation Channel situation > One path Transmission through a 2exceeding threshold (only one path having good situation path is good)Situation Channel situation > No path Duplicate transmission 3 exceedingthreshold (two applied paths are not good)

The UE 3 f-01 transmits an RRCConnectionReconfigurationComplete messagecontaining an identification message with respect to the SgNB 3 e-05 forURLLC or serving cell configuration (at step 3 f-40), and adds the SgNB3 e-05 for the URLLC or serving cell in accordance with theconfiguration value (at step 3 f-45). If data is generated in the URLLCbearer (at step 3 f-50), the UE 3 f-01 determines what transmission typeit performs data transmission/reception based on the channel measurementvalue for determining the transmission method received from the eNB 3f-03 and the current channel situation (at step 3 f-55). That is, the UE3 f-01 determines the operation method in accordance with the situationin the Table as described above. Whether to generate the URLLC data isdetermined by an upper layer (application), and the upper layerindicates the UE 3 f-01 whether to use the URLLC bearer.

If the channel situation is Situation 1, the UE 3 f-01 performstransmission through a preferred path pre-received from the eNB 3 f-03or a pre-transmittable path. Further, in case of Situation 2, the UE 3f-01 determines one transmission path having good channel situation fordata transmission/reception, and in case of Situation 3, the UE 3 f-01grasps that it is in the URLLC mode, and uses both the two paths throughapplying of the packet duplicate transmission. That is, at step 3 f-60,the UE 3 f-01 performs data transmission/reception through oneconfigured path of eNB 3 f-03 or SgNB 3 e-05, or performs packetduplicate transmission using both the two paths if the packetduplication is determined.

FIG. 3G is a diagram of a first operation of UE, according to anembodiment.

A UE configures a connection with an eNB for data transmission/reception(at step 3 g-05), and receives an RRC message containing SgNBconfiguration for URLLC from the eNB. The SgNB bearer is a bearerconfigured for the URLLC transmission, and an additional LCG cell groupand a serving cell may be configured. The configuration may differdepending on whether the duplicate transmission is the duplicatetransmission using the multi-connection or the duplicate transmissionusing the carrier aggregation. Further, in accordance with theconfiguration value, the SgNB for the URLLC or serving cell is added andconfigured (at step 3 g-10). The UE may report the measurement value ofthe downlink signal strength of serving cells to the eNB (at step 3g-15).

Thereafter, the UE receives a message including information forconfiguring a reference channel situation required to determine thetransmission method from the eNB (at step 3 g-20). The message mayinclude a preferred path for Situation 1 and threshold information fordetermining the channel situation in Table 5. Through the message, theeNB may clearly indicate transmission type 1 indicating what path datatransmission/reception should be performed, or may indicate to use boththe two paths through packet duplication in the URLLC mode since thetransmission channel state is not good. At step 3 g-25, the UE performsdata transmission/reception through one configured path of eNB/MgNB orSgNB in accordance with the indicated transmission type, or performspacket duplicate transmission using both the two paths if the packetduplication is determined.

FIG. 3H is a diagram of a second operation of UE, according to anembodiment.

A UE configures a connection with an eNB for data transmission/reception(at step 3 h-05), and receives an RRC message containing SgNBconfiguration for URLLC from the eNB. The SgNB bearer is a bearerconfigured for the URLLC transmission, and an additional LCG cell groupand a serving cell may be configured. The configuration may differdepending on whether the duplicate transmission is the duplicatetransmission using the multi-connection or the duplicate transmissionusing the carrier aggregation. In accordance with the configurationvalue, the UE adds and configures the SgNB for the URLLC or serving cellor channel situation reference (at step 3 h-10).

If data is generated in the URLLC bearer (at step 3 h-15), the UEdetermines what transmission type it performs datatransmission/reception based on the channel measurement value fordetermining the transmission method received from the eNB and thecurrent channel situation (at step 3 h-20). That is, the UE determinesthe operation method in accordance with the situation in the Table 6 asdescribed above. Whether to generate the URLLC data is determined by anupper layer (application), and the upper layer indicates the UE whetherto use the URLLC bearer. At step 3 h-25, the UE may perform datatransmission/reception through one configured path of the eNB/MgNB orSgNB in accordance with the determined transmission type, or may performpacket duplicate transmission using both the two paths if the packetduplication is determined.

FIG. 3I is a diagram of a terminal, according to an embodiment.

The terminal includes a RF processor 3 i-10, a baseband processor 3i-20, a storage unit 3 i-30, and a controller 3 i-40.

The RF processor 3 i-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. The RFprocessor 3 i-10 performs up-conversion of a baseband signal providedfrom the baseband processor 3 i-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 3 i-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the terminal may be providedwith a plurality of antennas. The RF processor 3 i-10 may include aplurality of RF chains. The RF processor 3 i-10 may perform beamforming.For the beamforming, the RF processor 3 i-10 may adjust phases and sizesof signals transmitted or received through the plurality of antennas orantenna elements. The RF processor may perform MIMO, and may receiveseveral layers during performing of a MIMO operation.

The baseband processor 3 i-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the system. During data transmission, the baseband processor 3 i-20generates complex symbols by encoding and modulating a transmitted bitstring. During data reception, the baseband processor 3 i-20 restores areceived bit string by demodulating and decoding the baseband signalprovided from the RF processor 3 i-10. When following an OFDM method,during data transmission, the baseband processor 3 i-20 generatescomplex symbols by encoding and modulating a transmitted bit string,performs mapping of the complex symbols on subcarriers, and thenconfigures OFDM symbols through the IFFT operation and CP insertion.During data reception, the baseband processor 3 i-20 divides thebaseband signal provided from the RF processor 3 i-10 in the unit ofOFDM symbols, restores the signals mapped on the subcarriers through theFFT operation, and then restores the received bit string throughdemodulation and decoding.

The baseband processor 3 i-20 and the RF processor 3 i-10 transmit andreceive the signals as described above. The baseband processor 3 i-20and the RF processor 3 i-10 may be called a transmitter, a receiver, atransceiver, or a communication unit. In order to support differentradio connection technologies, at least one of the baseband processor 3i-20 and the RF processor 3 i-10 may include a plurality ofcommunication modules. In order to process signals of differentfrequency bands, at least one of the baseband processor 3 i-20 and theRF processor 3 i-10 may include different communication modules. Thedifferent radio connection technologies may include a wireless LAN(e.g., IEEE 802.11) and a cellular network (e.g., LTE). Further, thedifferent frequency bands may include SHF (e.g., 2.NRHz or NRHz) bandand millimeter wave (mmWave) (e.g., 60 GHz) band.

The storage unit 3 i-30 stores a basic program for an operation of theterminal, application programs, and data of setup information. Inparticular, the storage unit 3 i-30 may store information related to aconnection node for performing wireless communication using a secondwireless connection technology. Further, the storage unit 3 i-30provides stored data in accordance with a request from the controller 3i-40.

The controller 3 i-40 controls the operation of the terminal. Thecontroller 3 i-40 transmits and receives signals through the basebandprocessor 3 i-20 and the RF processor 3 i-10. The controller 3 i-40records or reads data in or from the storage unit 3 i-30. The controller3 i-40 may include at least one processor. The controller 3 i-40 mayinclude a communication processor performing a control for communicationand an AP controlling an upper layer, such as an application program.The controller 3 i-40 may include a multi-connection processor 3 i-42for performing a process to operate in a multi-connection mode.

FIG. 3J is a diagram of a base station, according to an embodiment.

The base station includes an RF processor 3 j-10, a baseband processor 3j-20, a backhaul communication unit 3 j-30, a storage unit 3 j-40, and acontroller 3 j-50.

The RF processor 3 j-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. That is, theRF processor 3 j-10 performs up-conversion of a baseband signal providedfrom the baseband processor 3 j-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 3 j-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the base station may beprovided with a plurality of antennas. The RF processor 3 j-10 mayinclude a plurality of RF chains. The RF processor 3 j-10 may performbeamforming. For the beamforming, the RF processor 3 j-10 may adjustphases and sizes of signals transmitted or received through theplurality of antennas or antenna elements. Further, the RF processor mayperform down MIMO operation through transmission of one or more layers.

The baseband processor 3 j-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the first radio connection technology. During data transmission, thebaseband processor 3 j-20 generates complex symbols by encoding andmodulating a transmitted bit string. During data reception, the basebandprocessor 3 j-20 restores a received bit string by demodulating anddecoding the baseband signal provided from the RF processor 3 j-10. Forexample, when following an OFDM method, during data transmission, thebaseband processor 3 j-20 generates complex symbols by encoding andmodulating a transmitted bit string, performs mapping of the complexsymbols on subcarriers, and then configures OFDM symbols through theIFFT operation and CP insertion. During data reception, the basebandprocessor 3 j-20 divides the baseband signal provided from the RFprocessor 3 j-10 in the unit of OFDM symbols, restores the signalsmapped on the subcarriers through the FFT operation, and then restoresthe received bit string through demodulation and decoding. The basebandprocessor 3 j-20 and the RF processor 3 j-10 transmit and receive thesignals as described above. Accordingly, the baseband processor 3 j-20and the RF processor 3 j-10 may be called a transmitter, a receiver, atransceiver, or a wireless communication unit.

The backhaul communication unit 3 j-30 provides an interface forperforming communication with other nodes in the network. That is, thebackhaul communication unit 3 j-30 converts a bit string transmittedfrom the eNB to another node, for example, an auxiliary base station ora core network, into a physical signal, and converts a physical signalreceived from another node into a bit string.

The storage unit 3 j-40 stores a basic program for an operation of themain base station, application programs, and data of setup information.The storage unit 3 j-40 may store information on a bearer allocated tothe connected terminal and the measurement result reported from theconnected terminal. Further, the storage unit 3 j-40 may storeinformation that becomes a basis of determination whether to provide orsuspend a multi-connection to the terminal. Further, the storage unit 3j-40 provides stored data in accordance with a request from thecontroller 3 j-50.

The controller 3 j-50 controls the operation of the base station. Forexample, the controller 3 j-50 transmits and receives signals throughthe baseband processor 3 j-20 and the RF processor 3 j-10 or through thebackhaul communication unit 3 j-30. The controller 3 j-50 records orreads data in or from the storage unit 3 j-40. The controller 3 j-50 mayinclude at least one processor. The controller 3 j-50 may include amulti-connection processor 3 j-52 for performing a process to operate ina multi-connection mode.

FIG. 4A is a diagram of a next-generation mobile communication system,according to an embodiment.

Referring to FIG. 4A, a RAN of a next-generation mobile communicationsystem is composed of an NR NB 4 a-10 and an NR CN 4 a-05. NR UE orterminal 4 a-15 accesses to an external network through the NR NB 4 a-10and the NR CN 4 a-05.

In FIG. 4A, the NR NB 4 a-10 corresponds to an eNB of the existing LTEsystem. The NR NB is connected to the NR UE 4 a-15 on a radio channel,and thus it can provide a superior service than the service of theexisting node B. Since all user traffics are serviced on shared channelsin the next-generation mobile communication system, a device thatperforms scheduling through consolidation of status information, such asa buffer state of UEs, an available transmission power state, and achannel state, is required, and the NR NB 4 a-10 controls thisoperation.

One NR NB generally controls a plurality of cells. In order to implementultrahigh-speed data transmission as compared with the existing LTE, theNR NB may have a bandwidth that is greater than or equal to the existingmaximum bandwidth, and a beamforming technology may be additionallygrafted in consideration of OFDM as a RAT. Further, an AMC schemedetermining a modulation scheme and a channel coding rate to match thechannel state of the UE is applied. The NR CN 4 a-05 performs functionsof mobility support, bearer setup, and QoS configuration. The NR CN is adevice that controls not only a mobility management function of the UEbut also various kinds of control functions, and is connected to aplurality of eNBs. Further, the next-generation mobile communicationsystem may interlock with the existing LTE system, and the NR CN isconnected to an MME 4 a-25 through a network interface. The MME isconnected to an eNB 4 a-30 that is the existing eNB.

FIG. 4B is a diagram of a process of changing system information in anLTE technology, according to an embodiment.

System information broadcast by a base station is modified based on amodification period. In an LTE technology, the maximum value of themodification period is 10.24 sec. Excluding partial system information,newly changed system information may be broadcast from a time when eachmodification period starts. Further, in the previous modification periodbefore the newly changed system information is broadcast, terminals arenotified that the modified system information will be broadcast in anext modification period. If the modified system information isbroadcast from the (n+1)-th modification period 4 b-10, the terminalsare notified the fact that the system information is to be modified justin the previous n-th modification period 4 b-05. The base stationnotifies this using a paging message, and the terminal should receivethe paging at least once in the modification period.

If systemInfoModification IE is included in the paging message, thenewly updated system information is to be transmitted in a period nextto the modification period in which the paging is transmitted. If thesystem information is modified, excluding the partial systeminformation, a systemInfoValueTag value included in system informationblock (SIB) 1 is increased one by one. This may be used when theterminal camping on again in out-of coverage determines whether thesystem information stored therein is equal to the system informationbeing currently broadcast. The terminal may determine whether the systeminformation is modified using the paging message or thesystemInfoValueTag of the SIB1. For reduction of power consumption, if aDRX period is extended longer than the maximum value of the modificationperiod, the terminal may not receive the paging within the period.Further, when using an iterative transmission technique to extend aservice area, a longer time than the maximum value of the modificationperiod may be necessary to successfully decode the paging. It is notpossible to identify whether the system information is newly updated.Accordingly, a solution for identifying whether the system informationis newly updated solving this is necessary. In the LTE technology, if avery long DRX period is applied, or an iterative transmission techniqueis applied, a separate modification period is applied as shown in Table7 below.

TABLE 7 Use cases Modification Period (1) Normal case SFN mod m = 0 (2)For BL UEs and (H-SFN * 1024 + SFN) mod m = 0 UEs in CE (3) For UE ineDRX H-SFN mod 256 = 0 (called eDRX acquisition period) (4) For NB-IoTUE H-SFN mod 1024 = 0 (i.e. eDRX in eDRX acquisition period for NB-IoT)

When applying a very long DRX period or an iterative transmissiontechnique, the modification period used to update the system informationmay have a very long length, and securing that the terminal cansuccessfully decode the paging in the modification period. The specificmodification period is applied in accordance with specific featuresapplied by the terminal, that is, eMTC technology is used to extend theservice area (second use case in the above Table) or eDRX technology isused to provide a very long DRX period (third and fourth use cases inthe above Table). The length of the modification period applied to theeMTC technology can be configured, but the modification period appliedto the eDRX technology is unable to be configured and uses a fixedvalue. The lengths of all the modification periods are cell-specificvalues, and all the terminals applying the specific features apply themodification period having the same size.

FIG. 4C is a diagram of a method for performing SI validity check beforeRRC connection establishment when applying an eDRX technology in an LTEtechnology, according to an embodiment.

If the eDRX period is longer than the modification period being applied,the terminal may perform the method of FIG. 4C. The terminal receivespaging for a paging time window (PTW) time period 4 c-10 configured foreach eDRX period at step 4 c-05. After receiving the paging at step 4c-15 for the PTW period, if a paging record of the terminal is includedin the paging message, the terminal receives SIB1 being broadcast fromthe cell. The terminal identifies a value tag value included in thesystem information, and determines whether the value tag value is equalto a pre-stored value tag value. This operation is called SI validitycheck. If the values are different from each other, the terminalreceives the system information being broadcast from the cell before anRRC connection establishment (at step 4 c-20). If the paging record ofthe terminal is not included in the paging message, the terminal may notperform the SI validity check through reading of the SIB1. The pagingmessage should be successfully decoded, and if the paging configurationinformation provided as the system information is modified, the terminalmay not properly operate.

FIG. 4D is a diagram of a method for indicating whether an SI update isnecessary by transmitting a paging in an extended modification period incase of applying an eDRX technology in an LTE technology, according toan embodiment.

If the eDRX period is longer than the modification period being applied,the terminal may perform the method of FIG. 4D. The terminal receivespaging for a PTW time period at step 4 d-15 configured for each eDRXperiod at step 4 d-05. If a systemInfoModification-eDRX indicator isincluded in the paging message, the terminal performs SI updatingoperation from a specific time (at step 4 d-20). The indicator indicatesthat the updated SI is transmitted from the specific time. The timesatisfies H-SFN mod 256=0 (at step 4 d-10). Accordingly, the terminalperforms SI update from the time (at step 4 d-25). Through thereception, it can be determined that the time exists at a constantinterval, that is, every 256*10.24 sec, and at a newly extendedmodification period. At the constant interval, the terminal has anopportunity to receive the paging message at least once in the PTW.Since the base station transmits the paging message including theindicator for the extended modification period.

A method capable of minimizing unnecessary signaling overhead whenupdating the SI using the paging message in the long modification periodis provided.

FIG. 4E is a diagram of a plurality of modification periods, accordingto an embodiment. One or a plurality of network-configurablemodification periods can be determined. There exists an individualsystemInfoModification IE corresponding to each modification period.Further, an SI update notification method corresponding to eachmodification period can be signaled. For example, in a firstmodification period, a method using a paging message introduced in FIG.4D can be applied, and in a second modification period, both a methodfor identifying a value tag before configuring the establishmentintroduced in FIGS. 4C and 4D and a method using a paging message can beapplied.

The length and boundary of the plurality of modification periods areindicated based on a system frame number (SFN) at step 4 e-05. That is,SFN mod m=0, where m denotes the length of the modification period, andthe unit is one of a frame, subframe, TTI, and slot composed of one ormore OFDM symbols. The configuration information on the plurality ofmodification periods at steps 4 e-10, 4 e-15, 4 e-20, and 4 e-25 isbroadcast by a network using the system information. The lengths atsteps 4 e-30, 4 e-35, 4 e-40, and 4 e-45 of the plurality ofmodification periods has a common multiple relationship with each other.In the LTE technology in the related art, the terminal determines a usedmodification period among the above-described modification periods inaccordance with eMTC or eDRX. However, in the present disclosure, evenif a specific feature is applied, it is featured that the terminalselects and applies one of the plurality of designated modificationperiods. The network broadcasts as the system information configurationinformation of one or more modification periods that can be selected bya specific terminal, a terminal group, or a terminal applying a specificfeature. The terminal selects and applies one of modification periods inthe configuration information that the terminal can select in accordancewith a specific rule.

The specific rule considers a DRX period applied by the terminal, afeature applied by the terminal, or the kind of the terminal. Inconsideration of the features applied by the terminal, the firstmodification period at step 4 e-10 and the second modification period atstep 4 e-15 are modification periods that can be selected by a generalterminal, and the third modification at step period 4 e-20 and thefourth modification period at step 4 e-25 are modification periods thatcan be selected by a terminal applying the technology to extend a verylong DRX period or a service area.

When selecting the modification period, the terminal selects one of aplurality of existing selectable modification periods in accordance witha specific rule. As one of specific rules, proposed is a method forselecting the shortest one of modification periods that arelonger/greater than the applied DRX period among one or moremodification periods selectable by the terminal. A 5G base station canbe provided with DRX period information of terminals existing in atracking area from a next-generation core network (NGC). Based on theDRX period information, the 5G base station can grasp the shortestmodification period in which all terminals in the cell can receive thepaging. The base station transmits the paging indicating SI update forthe shortest modification period. This method can reduce the downlinksignaling overhead in comparison to the method for transmitting pagingindicating SI update for the maximum eDRX period in the LTE technologyin the related art.

FIG. 4F is a diagram of updating system information based on a pluralityof modification periods, according to an embodiment.

A base station 4 f-10 broadcasts one or more pieces of modificationperiod configuration information and an SI update notification methodcorresponding to each modification period using system information (atstep 4 f-15). The modification period configuration informationindicates whether only a specific terminal, a terminal group, or aterminal applying a specific feature can use them. The specific featuremay include a technology to apply a very long DRX period or an iterativetransmission technology for extending a service area. The terminal 4f-05, base station 4 f-10, and an NGC 4 f-13 interlock with each otherto determine a DRX period applied to the terminal (at step 4 f-20).

The terminal 4 f-05 grasps one or more modification periods that can beselected by the terminal 4 f-05 itself among one or more modificationperiods. The terminal 4 f-05 selects the shortest modification periodamong modification periods that are longer than the DRX period appliedby the terminal 4 f-05 itself (at step 4 f-25). The base station 4 f-10determines updating of the system information (at step 4 f-26). The basestation 4 f-10 requests the maximum DRX period value with respect toterminals existing in the tracking area from the NGC 4 f-13 (at step 4f-27). The NGC 4 f-13 provides the maximum DRX period value (at step 4f-28).

The base station 4 f-10 determines the modification period in which allterminals in the cell can receive the paging using the maximum DRXperiod information. The base station 4 f-10 transmits the paging messageindicating the SI update during the determined modification period (atstep 4 f-29). The paging message includes a systemInfoModification IEcorresponding to the determined modification period. The base station 4f-10 broadcasts the SI updated in the coming modification period (atstep 4 f-40). All terminals in the cell determine an accurate SIupdating time by deriving the modification period corresponding to thesystemInfoModification (at step 4 f-30). In the coming modificationperiod, the terminal 4 f-05 starts SI updating (at step 4 f-45). An SIupdate notification method corresponding to the modification period isapplied. For example, if a value tag has been configured, the terminal 4f-05 grasps whether the SI is the latest SI by identifying the value tagbefore establishment (at step 4 f-50).

FIG. 4G is a flowchart of a method of an operation of a terminal,according to an embodiment.

At step 4 g-05, a terminal receives from a base station one or morepieces of modification period configuration information and an SI updatenotification method corresponding to each modification period. At step 4g-10, the terminal selects a first modification period that is shortestamong modification periods that are longer than a DRX period applied bythe terminal itself. At step 4 g-15, the terminal determines whether apaging message is transmitted in the selected first modification period.At step 4 g-17, the terminal receives the paging message indicating SIupdate. At step 4 g-20, the terminal grasps a boundary of the secondmodification period corresponding to a systemInfoModification IEincluded in the paging message. At step 4 g-25, the terminal updates thesystem information at the coming boundary. At step 4 g-30, the terminalapplies an SI update notification method corresponding to the firstmodification period.

FIG. 4H is a flowchart of an operation of a base station, according toan embodiment.

At step 4 h-05, a base station broadcasts one or more pieces ofmodification period configuration information and an SI updatenotification method corresponding to each modification period usingsystem information. At step 4 h-10, the base station determines updatingof the system information. At step 4 h-15, the base station requests themaximum DRX period value among DRXs applied to terminals belonging to aspecific area, such as a tracking area, from an NGC. At step 4 h-20, thebase station receives the maximum DRX period value from the NGC. At step4 h-25, the base station selects the shortest second modification periodamong modification periods that are longer than the maximum DRX periodvalue. At step 4 h-30, the base station includes thesystemInfoModification IE corresponding to the second modificationperiod in the paging message indicating the SI update. At step 4 h-35,the base station repeatedly transmits the paging in the n-th secondmodification period. At step 4 h-40, the base station transmits theupdated system information from the (n+1)-th second modification period.

FIG. 4I is a diagram of a terminal, according to an embodiment.

The terminal includes an RF processor 4 i-10, a baseband processor 4i-20, a storage unit 4 i-30, and a controller 4 i-40.

The RF processor 4 i-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. The RFprocessor 4 i-10 performs up-conversion of a baseband signal providedfrom the baseband processor 4 i-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 4 i-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the terminal may be providedwith a plurality of antennas. The RF processor 4 i-10 may include aplurality of RF chains. The RF processor 4 i-10 may perform beamforming.For the beamforming, the RF processor 4 i-10 may adjust phases and sizesof signals transmitted or received through the plurality of antennas orantenna elements. The RF processor may perform MIMO, and may receiveseveral layers during performing of a MIMO operation.

The baseband processor 4 i-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the system. During data transmission, the baseband processor 4 i-20generates complex symbols by encoding and modulating a transmitted bitstring. During data reception, the baseband processor 4 i-20 restores areceived bit string by demodulating and decoding the baseband signalprovided from the RF processor 4 i-10. For example, when following OFDMmethod, during data transmission, the baseband processor 4 i-20generates complex symbols by encoding and modulating a transmitted bitstring, performs mapping of the complex symbols on subcarriers, and thenconfigures OFDM symbols through the IFFT operation and CP insertion.During data reception, the baseband processor 4 i-20 divides thebaseband signal provided from the RF processor 4 i-10 in the unit ofOFDM symbols, restores the signals mapped on the subcarriers through theFFT operation, and then restores the received bit string throughdemodulation and decoding.

The baseband processor 4 i-20 and the RF processor 4 i-10 transmit andreceive the signals as described above. The baseband processor 4 i-20and the RF processor 4 i-10 may be called a transmitter, a receiver, atransceiver, or a communication unit. In order to support differentradio connection technologies, at least one of the baseband processor 4i-20 and the RF processor 4 i-10 may include a plurality ofcommunication modules. In order to process signals of differentfrequency bands, at least one of the baseband processor 4 i-20 and theRF processor 4 i-10 may include different communication modules. Thedifferent radio connection technologies may include a wireless LAN(e.g., IEEE 802.11) and a cellular network (e.g., LTE). The differentfrequency bands may include SHF (e.g., 2.NRHz or NRHz) band andmillimeter wave (mmWave) (e.g., 60 GHz) band.

The storage unit 4 i-30 stores a basic program for an operation of theterminal, application programs, and data of setup information. Thestorage unit 4 i-30 may store information related to a connection nodefor performing wireless communication using a second wireless connectiontechnology. The storage unit 4 i-30 provides stored data in accordancewith a request from the controller 4 i-40.

The controller 4 i-40 controls the operation of the terminal. Thecontroller 4 i-40 transmits and receives signals through the basebandprocessor 4 i-20 and the RF processor 4 i-10. The controller 4 i-40records or reads data in or from the storage unit 4 i-30. The controller4 i-40 may include at least one processor. The controller 4 i-40 mayinclude a communication processor performing a control for communicationand an AP controlling an upper layer, such as an application program.The controller 4 i-40 may include a multi-connection processor 4 i-42for performing a process to operate in a multi-connection mode.

FIG. 4J is a diagram of a base station, according to an embodiment.

The base station includes an RF processor 4 j-10, a baseband processor 4j-20, a backhaul communication unit 4 j-30, a storage unit 4 j-40, and acontroller 4 j-50.

The RF processor 4 j-10 transmits and receives a signal through a radiochannel, such as signal band conversion and amplification. That is, theRF processor 4 j-10 performs up-conversion of a baseband signal providedfrom the baseband processor 4 j-20 into an RF-band signal to transmitthe converted signal to an antenna, and performs down-conversion of theRF-band signal received through the antenna into a baseband signal. TheRF processor 4 j-10 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.Although only one antenna is illustrated, the base station may beprovided with a plurality of antennas. Further, the RF processor 4 j-10may include a plurality of RF chains. The RF processor 4 j-10 mayperform beamforming. For the beamforming, the RF processor 4 j-10 mayadjust phases and sizes of signals transmitted or received through theplurality of antennas or antenna elements. The RF processor may performdown MIMO operation through transmission of one or more layers.

The baseband processor 4 j-20 performs conversion between a basebandsignal and a bit string in accordance with the physical layer standardof the first radio connection technology. During data transmission, thebaseband processor 4 j-20 generates complex symbols by encoding andmodulating a transmitted bit string. During data reception, the basebandprocessor 4 j-20 restores a received bit string by demodulating anddecoding the baseband signal provided from the RF processor 4 j-10. Forexample, when following an OFDM method, during data transmission, thebaseband processor 4 j-20 generates complex symbols by encoding andmodulating a transmitted bit string, performs mapping of the complexsymbols on subcarriers, and then configures OFDM symbols through theIFFT operation and CP insertion. During data reception, the basebandprocessor 4 j-20 divides the baseband signal provided from the RFprocessor 4 j-10 in the unit of OFDM symbols, restores the signalsmapped on the subcarriers through the FFT operation, and then restoresthe received bit string through demodulation and decoding. The basebandprocessor 4 j-20 and the RF processor 4 j-10 transmit and receive thesignals as described above. The baseband processor 4 j-20 and the RFprocessor 4 j-10 may be called a transmitter, a receiver, a transceiver,or a wireless communication unit.

The backhaul communication unit 4 j-30 provides an interface forperforming communication with other nodes in the network. The backhaulcommunication unit 4 j-30 converts a bit string transmitted from the eNBto another node, for example, an auxiliary base station or a corenetwork, into a physical signal, and converts a physical signal receivedfrom another node into a bit string.

The storage unit 4 j-40 stores a basic program for an operation of themain base station, application programs, and data of setup information.The storage unit 4 j-40 may store information on a bearer allocated tothe connected terminal and the measurement result reported from theconnected terminal. The storage unit 4 j-40 may store information thatbecomes a basis of determination whether to provide or suspend amulti-connection to the terminal. The storage unit 4 j-40 providesstored data in accordance with a request from the controller 4 j-50.

The controller 4 j-50 controls the base station. The controller 4 j-50transmits and receives signals through the baseband processor 4 j-20 andthe RF processor 4 j-10 or through the backhaul communication unit 4j-30. The controller 4 j-50 records or reads data in or from the storageunit 4 j-40. The controller 4 j-50 may include at least one processor.The controller 4 j-50 may include a multi-connection processor 4 j-52for performing a process to operate in a multi-connection mode.

The methods and apparatuses described herein may be implemented in theform of hardware, software, or a combination of hardware and software.

In case of software implementation, a non-transitory computer readablestorage medium storing one or more programs (software modules) may beprovided. One or more programs stored in the computer readable storagemedium are configured for execution by one or more processors in anelectronic device. The one or more programs include instructionsinstructing the electronic device to execute the methods according tothe embodiments described in claims and the description.

Such programs (software modules or software) may be stored in a randomaccess memory (RAM), nonvolatile memory including a flash memory, readonly memory (ROM), electrically erasable programmable read only memory(EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM),digital versatile discs (DVDs) or other types of optical storagedevices, and magnetic cassette. Further, the programs may be stored in amemory composed of a combination of parts or the whole thereof. Further,a plurality of constituent memories may be included.

Further, the programs may be stored in an attachable storage devicecapable of accessing through communication networks, such as Internet,Intranet, local area network (LAN), wide LAN (WLAN), and storage areanetwork (SAN), or communication networks composed of combinationsthereof. Such a storage device may be connected to a device performingthe methods described herein through an external port. Further, aseparate storage device on the communication network may be connected tothe device performing the methods described herein.

While the disclosure has been shown and described with reference tocertain embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the scope of the disclosure. Therefore, the scopeof the disclosure should not be defined as being limited to theembodiments, but should be defined by the appended claims andequivalents thereof.

What is claimed is:
 1. A method performed by a transmitting device in awireless communication system, the method comprising: obtaining a radiolink control (RLC) service data unit (SDU) from an upper layer;generating an unacknowledged mode (UM) data (UMD) protocol data unit(PDU) for the RLC SDU, the UMD PDU including a UMD PDU header; andtransmitting the UMD PDU to a receiving device, wherein the UMD PDUheader includes a segmentation information (SI) field and a reserved (R)field, in case that the UMD PDU includes a complete RLC SDU, which isthe RLC SDU, and wherein the UMD PDU header includes an SI field, an Rfield and a sequence number (SN) field, in case that the UMD PDUincludes an RLC SDU segment, which is a segment of the RLC SDU.
 2. Themethod of claim 1, wherein the UMD PDU header further includes a segmentoffset (SO) field, in case that the RLC SDU segment includes a middlesegment of the RLC SDU or a last segment of the RLC SDU, and wherein theUMD PDU header does not include an SO field, in case that the RLC SDUsegment includes a first segment of the RLC SDU.
 3. The method of claim1, wherein the UMD PDU header is byte aligned and the UMD PDU headerconsists of 2 bits of the SI field and 6 bits of the R field, in casethat the UMD PDU includes the complete RLC SDU.
 4. The method of claim1, wherein the UMD PDU header is byte aligned and the UMD PDU headerconsists of 2 bits of the SI field, 2 bits of the R field and 12 bits ofthe SN field, in case that the UMD PDU includes the RLC SDU segment. 5.The method of claim 4, wherein a length of the SN field is configured touse 12 bits through a radio resource control (RRC) signaling.
 6. Amethod performed by a receiving device in a wireless communicationsystem, the method comprising: receiving, from a transmitting device, anunacknowledged mode (UM) data (UMD) protocol data unit (PDU) for a radiolink control (RLC) service data unit (SDU), the UMD PDU including a UMDPDU header; and identifying a UMD PDU header from the UMD PDU, whereinthe UMD PDU header includes a segmentation information (SI) field and areserved (R) field, in case that the UMD PDU includes a complete RLC SDUwhich is the RLC SDU, and wherein the UMD PDU header includes an SIfield, an R field and a sequence number (SN) field, in case that the UMDPDU includes an RLC SDU segment which is a segment of the RLC SDU. 7.The method of claim 6, wherein the UMD PDU header further includes asegment offset (SO) field, in case that the RLC SDU segment includes amiddle segment of the RLC SDU or a last segment of the RLC SDU, andwherein the UMD PDU header does not include an SO field, in case thatthe RLC SDU segment includes a first segment of the RLC SDU.
 8. Themethod of claim 6, wherein the UMD PDU header is byte aligned and theUMD PDU header consists of 2 bits of the SI field and 6 bits of the Rfield, in case that the UMD PDU includes the complete RLC SDU.
 9. Themethod of claim 6, wherein the UMD PDU header is byte aligned and theUMD PDU header consists of 2 bits of the SI field, 2 bits of the R fieldand 12 bits of the SN field, in case that the UMD PDU includes the RLCSDU segment.
 10. The method of claim 9, wherein a length of the SN fieldis configured to use 12 bits through a radio resource control (RRC)signaling.
 11. A transmitting device in a wireless communication system,the transmitting device comprising: a transceiver; and a controllerconfigured to: obtain a radio link control (RLC) service data unit (SDU)from an upper layer, generate an unacknowledged mode (UM) data (UMD)protocol data unit (PDU) for the RLC SDU, the UMD PDU including a UMDPDU header, and transmit the UMD PDU to a receiving device via thetransceiver, wherein the UMD PDU header includes a segmentationinformation (SI) field and a reserved (R) field, in case that the UMDPDU includes a complete RLC SDU which is the RLC SDU, and wherein theUMD PDU header includes an SI field, an R field and a sequence number(SN) field, in case that the UMD PDU includes an RLC SDU segment whichis a segment of the RLC SDU.
 12. The transmitting device of claim 11,wherein the UMD PDU header further includes a segment offset (SO) field,in case that the RLC SDU segment includes a middle segment of the RLCSDU or a last segment of the RLC SDU, and wherein the UMD PDU headerdoes not include an SO field, in case that the RLC SDU segment includesa first segment of the RLC SDU.
 13. The transmitting device of claim 11,wherein the UMD PDU header is byte aligned and the UMD PDU headerconsists of 2 bits of the SI field and 6 bits of the R field, in casethat the UMD PDU includes the complete RLC SDU.
 14. The transmittingdevice of claim 11, wherein the UMD PDU header is byte aligned and theUMD PDU header consists of 2 bits of the SI field, 2 bits of the R fieldand 12 bits of the SN field, in case that the UMD PDU includes the RLCSDU segment.
 15. The transmitting device of claim 14, wherein a lengthof the SN field is configured to use 12 bits through a radio resourcecontrol (RRC) signaling.
 16. A receiving device in a wirelesscommunication system, the receiving device comprising: a transceiver;and a controller configured to: receive, from a transmitting device viathe transceiver, an unacknowledged mode (UM) data (UMD) protocol dataunit (PDU) for a radio link control (RLC) service data unit (SDU), theUMD PDU including a UMD PDU header, and identify a UMD PDU header fromthe UMD PDU, wherein the UMD PDU header includes a segmentationinformation (SI) field and a reserved (R) field, in case that the UMDPDU includes a complete RLC SDU which is the RLC SDU, and wherein theUMD PDU header includes an SI field, an R field and a sequence number(SN) field, in case that the UMD PDU includes an RLC SDU segment whichis a segment of the RLC SDU.
 17. The receiving device of claim 16,wherein the UMD PDU header further includes a segment offset (SO) field,in case that the RLC SDU segment includes a middle segment of the RLCSDU or a last segment of the RLC SDU, and wherein the UMD PDU headerdoes not include an SO field, in case that the RLC SDU segment includesa first segment of the RLC SDU.
 18. The receiving device of claim 16,wherein the UMD PDU header is byte aligned and the UMD PDU headerconsists of 2 bits of the SI field and 6 bits of the R field, in casethat the UMD PDU includes the complete RLC SDU.
 19. The receiving deviceof claim 16, wherein the UMD PDU header is byte aligned and the UMD PDUheader consists of 2 bits of the SI field, 2 bits of the R field and 12bits of the SN field, in case that the UMD PDU includes the RLC SDUsegment.
 20. The receiving device of claim 19, wherein a length of theSN field is configured to use 12 bits through a radio resource control(RRC) signaling.